If your opponent continues to massively produce Marines or Firebats during the later stages of the game, use Ultralisks to mow through the enemy infantry lines. If the Ultralisk's Carapace is fully upgraded, the Marines and Firebats will inflict very little damage. Even a single Ultralisk can destroy entire squads at a time. The fast and long ranged attack of the Guardian will also annihilate Terran infantry in an effective manner.

Vultures
Vultures can be a nuisance to a Zerg force with their quick speed and Spider Mines, but their power should not be underestimated. Vultures have the capability to execute quick hit and run raids against your Drones, and the Vulture's attack does excellent damage to the small Zerglings. Fields of Spider Mines also prove fairly nasty to an unsuspecting Zergling attack force. Masses of Hydralisks have little to fear from either the Vultures or Spider Mines, but the speed of the Vulture usually allows the Terran to retreat from any engagement. The best counter to the Vulture is the Mutalisk. Since the Vulture has no anti-air capability, the hover bikes make easy targets for the fast moving Mutalisks.

Siege Tanks
Siege Tanks are a rather powerful component of the Terran arsenal. Siege Tanks in Siege Mode protected by Bunkers and Missile Turrets can be annoyingly difficult to uproot. The Zerg Swarm does have quite a few counters available for the power of the Siege Tank.

The single best counter to a Siege Tank is the Queen's Spawn Broodling ability. Each use of this ability will instantly destroy a Siege Tank. A group of Queens can quickly clear out an entire Tank blockade. Since the ability is reusable, Queens only need to recharge their energy before being able to wreak havoc against more Siege Tanks. When using Spawn Broodling, be sure to pick the Tanks that are in the middle of a Tank group or right next to a Bunker or Missile Turret. As soon as that Tank is destroyed, any other Tanks within range will open fire on the Broodlings in their midst. The Siege Tank fire will cause splash damage to any units that are nearby, friendly or not.

Another solution for the Siege Tank is the combination of Dark Swarm and Zerglings. Once covered with Dark Swarm, Siege Tanks will be unable to inflict direct damage (although Siege Mode will still cause considerable splash damage) to the incoming Zerglings. Nearby Bunkers will be unable to deal with the Zergling threat as long as the Dark Swarm remains over the Zerglings. Zerglings with the Adrenal Gland upgrade can quickly dispatch any Terran unit or buildings beneath the cloud.

If the timing of this combined attack proves too tricky, use Guardians against enemy Siege Tanks. Their superior attack range ensures that any nearby Bunkers or Missile Turrets will be insufficient to stop the Guardian attack. Unless there are Wraiths, Valkyries or Battlecruisers nearby, the Guardians will quickly ravage any Siege Tanks present.

Prevent Offensive Bunkering
A sneaky tactic the Zerg must watch for in the early to mid game is the use of offensive Bunkers possibly supported by Siege Tanks. These blockades can easily pin a Zerg colony and allow the Terran to expand unimpeded across the rest of the battlefield. Unless the blockade is broken, the Terrans will also continue to extend the defensive web into the very heart of your Brood. The best and simplest counter to these tactics is to prevent the blockade from even being built. Use Zerglings and Drones to keep an eye on the area near the colony to keep it free of any Terran presence. Should a Terran attempt to pull an offensive bunker maneuver in the late game, use Guardians to quickly smash the attempt. If you don't have any Guardians, Queens can use their Spawn Broodling ability on the SCVs constructing the Terran defenses. You can then send in waves of Hydralisks and Zerglings to crush the Terran.

[ Click to Enlarge - 87 KB ] Terrans assualt a Zerg Town using a Siege Tank and Marines in a Bunker with a repairing SCV.	[ Click to Enlarge - 94 KB ] Hydralisks rush to defend the Hive using sheer numbers to overwhelm the invasion force.

Goliaths
The Terran Goliath is a deadly threat to Overlords, Guardians and Devourers, particularly if the Goliaths have been upgraded with Charon Boosters (increased attack range). The explosive antiair weaponry of the Goliath does not fare as well against Mutalisks, but overwhelming numbers of Goliaths and the long range of Charon Boosters can hide this weakness. The primary problems of the Goliath are the slow firing ground attack and the large size of the vehicle itself. Both Zerglings and Hydralisks prove effective weapons against a Goliath army.

Cloaked Wraiths
Cloaked Wraiths in the hands of a competent Terran commander can prove quite a thorn in the side of the Zerg. Although Overlords can easily detect their presence, Cloaked Wraiths can also kill an Overlord in a matter seconds. If you know there are Cloaked Wraiths around, keep a large group of Overlords with your attack forces at all times. Wraiths are surprisingly fragile and are easily driven off by Hydralisks if the Wraiths cannot overcome the nearby detector presence.

To provide defense for your bases, set up Spore Colonies to both detect and repel Cloaked Wraiths.

[ Click to Enlarge - 92 KB ] This Zerg player has no anti-air defenses making this setup ripe for a Cloaked Wraith attack. Place Spore Colonies and/or Hydralisks along with your other units.

Valkyries
The Terran Valkyrie is a fairly recent addition to the Terran air force, and a rather unwelcome one from the Zerg perspective. Their cluster missiles damage all air units in a target area and can quickly annihilate groups of Overlords or Mutalisks with a minimum of effort. Fortunately Valkyries are slow moving and make prime targets for Scourge and Hydralisks. Hydralisks have nothing to fear from the Valkyrie since the Valkyrie has no ability to attack ground unit. Scourge can strike Valkyries before they have a chance to unleash their missile volleys.

Irradiate
Irradiate is one of the deadliest threats to the Zerg. An Irradiated Overlord is guaranteed to die (unless a Terran Medic uses Restoration to cure it.) Tightly grouped or stacked groups of Hydralisks, Zerglings, Mutalisks, or Guardians take heavy damage from an Irradiate. Whenever a Science Vessel is spotted, destroy the blasted thing immediately with Scourge. Should your forces encounter a Science Vessel, try to spread them out to reduce the effects of Irradiate. Equip your Hydralisk horde with Burrowing to help combat Irradiate. An irradiated Hydralisk will surely die even if burrowed, but burrowing the Hydralisk does prevent the Irradiation field from damaging other nearby Zerg units.

[ Click to Enlarge - 88 KB ] Irradiated Overlords ensure that the Zerg detection abilities will soon diminish giving these Cloaked Wraiths a better chance of destroying the Zerg force.	[ Click to Enlarge - 94 KB ] Irradiate can cause heavy damage to packs of Hydralisks and with this many Science Vessels, multiple Irradiations can quickly destroy the invaders.

Battlecruiser Fleets
Battlecruisers are quite possibly the most fearsome unit in the game. In large numbers they can be nearly unstoppable. To counter them, you'll need to use a combination of special abilities and your air and ground forces to defeat them. Since the Battlecruiser moves rather slowly, you should always have some time to set up a good defense after the Battlecruisers reach your outside picket lines. The Defiler's Plague will reduce their HP rapidly while a Queen's Ensnare will slow down the Battlecruisers to a snail's pace and prevent retreat. Follow up with the Acid Spore attack of your Devourers, increasing the amount of damage they take per hit and increasing their weaponry's cooldown. Finish them off with Mutalisks, or use Hydralisks protected beneath a Dark Swarm. If the Battlecruisers weaponry is already distracted with other units, Scourge can even be used.

The main key to completely defeating a Battlecruiser fleet is not allowing the ships to retreat back to their home base. Should the Battlecruisers make it back safely, they can be repaired and back at full strength within a few minutes.

Infesting Command Centers
It's often easy to forget, but the Terrans provide a unique opportunity for the Zerg. Should one of their Command Centers be severely damaged the Zerg Queen can infest it and bring it under the control of the Zerg. These Infested Command Centers can produce Infested Terrans bound completely to the Zerg will. Infested Terrans work particularly well when attacking lone Terran Bunkers and any other unprotected Terran structures on the ground.

To infest the Command Center, simply place a Queen near the Command Center. As soon as the building becomes damaged enough, the Queen will automatically move in and infest it.

Remember that as soon as a Command Center is infested, any nearby Terran defenses will immediately treat it as an enemy presence and open fire. If possible, infest Command Centers that are not too heavily defended. As soon as the Command Center is infested, lift your new building off and fly it to a safe haven where you can begin producing Infested Terrans.