StarCraft: Brood War/Zerg Mission 9: The Reckoning

Getting started
In this mission, you start with a large base with a full tech tree along with adequate defenses. You won't have to worry about building additional to your base, since the UED attacks are almost negligeable and the Protoss will not harass your base at all. In fact, many of your starting units should be used for the attack. Just make sure you have a few Hydralisks left in your base (3 per side is enough). You are also given many mineral fields, so minerals will probably be the least of your concern. This mission may go very smoothly, or will result in many of your units killed, depending on how you plan it out.

Start by building lots of drones. You want to thoroughly exploit your resources since you probably don't have time to conquer more and you won't mine it out in 30 minutes either. Because you have just one geyser, gas will be your limiting factor for most of the mission. If you absolutely need more gas, you should use your initial forces to take out the UED in the south, where there is another geyser. Finally, because you have limited time, you will need to start upgrading as early as possible. Start by buying Ventral Sacs (Overlord transport) and Pneumatized Carapace (speed). Zerglings with Adrenal Glands (attack speed) are also great for demolishing buildings. Finally, send your guardians to the plateau with the stasis cell to clear it out. These photon cannons are inaccessible except by air, and you don't want to leave them for last.

There are two land routes to the Protoss base. The one north of your base takes you past a Terran base, including some inconvenient Siege Tanks and Bunkers. The route to the south is much less defended. You could airdrop your units, but there is an even better strategy. The startegy is to airlift a drone over to the west side of the Protoss and build a Hatchery, followed by a Nydus Canal. Order your hatcheries to rally to this canal, so that reinforcements will go straight to your new base. Now you're ready to attack.

The Attack
It will take at least 5 minutes to destroy the base, and more if your first attempt fails and you need to build another wave. The best thing to do is to plan an attack that will not completely fail the first time. Try to attack around the 10-minute mark, or even earlier if you want the bonus mission.

Hydralisks are good against most of the Protoss units, but Zerglings are cheap and come in bulk. Get two groups of each before you launch your assault. Also, get at least 6 Scourges; the Protoss have a Carrier and you don't want to mess with it. Your Zerglings are expendable, so have them swarm the Reavers, Archons, and High Templars so that your Hydralisks can do some real damage (Your starting Ultralisk is also good for this, but vulnerable to Mind Control). Also, remember to bring Overlords for detection against Dark Templars. The UED loves to blind your Overlords, so make sure they can still see. As you attack, keep cranking out Hydralisks and Zerglings at your home base. Protoss resistance is stiff and you may need several waves. It's okay to pull away defenders from your base, as the Terran attacks are pathetic.

You can also build a few more Guardians to protect your ground units, should Reavers, Dark Templars and Archons be a huge concern. They are also very good against Photon Cannons, so let them take out the heavy ground defenders.

If you keep losing your attack force, try a "defensive" attack. Burrow lurkers in front of your proxy base and also build a sunken colony. Send a couple of units to draw out the Protoss (your guardians work well) and kill them as they approach, then charge once you've thinned their numbers. The only caveat is that High Templar will slaughter your tightly-packed defenders.