StarCraft/Zerg mission 6: The Dark Templar

Establishing Your Base
You start with a modest defense force of four Hydralisks, two Mutalisks, two Guardians, and Kerrigan. Guardians are new, and they're basically bombers. One gob of their acid deal 20 explosive damage, and their range beats those of any stationary defense. However, they have no air attack and thus must be protected if they're to stay alive long enough to be worth their high cost (you're paying 100 minerals and 100 gas for a Mutalisk, then 50 minerals and 100 gas to upgrade it to a Guardian).

You have a lot of minerals at your disposal, but you'll definitely need more gas. Fortunately, there are two very large resource deposits near you: one to the east and one to the south. They're both plateaus, inaccessible by ground, and a small Protoss force guards the southern deposit. Explore both of these locations with the Mutalisks you start with so you know where they are.

Meanwhile, build a healthy number of Drones for resource gathering, and when you have a steady income start building static defense as well as some Hydralisks (also, as you're doing this try to upgrade your Hatchery to a Lair and upgrade Overlord Transport). There are two ramps that lead to your base, and each needs to be protected by two or three Sunken Colonies. Place about four Spore Colonies at regular intervals along the southern edge of your base, and station any Hydralisks you make near the ramps. This will give you a solid defense, and the small Protoss attacks that occur periodically will not bother you.

Now, build a Spire. You need a Lair to do this, so upgrade that Hatchery if you haven't yet. Start churning out some Mutalisks, and as soon as you have about four Mutalisks and Overlord Transport researched, load Kerrigan, three Drones, and two Hydralisks onto an Overlord and start building an expansion base on the unguarded resource deposit to the east. Station every Mutalisk you make from now on at this base; ground units can't really defend it. These resources should be enough for you to finish the mission with.