Here's one way. Split your army into two parts, melee units and ranged units. Set the melee units to ctrl-1 and the ranged to ctrl-2. Have your melee units go one way and your ranged another, and use them to flank and sandwich the enemy army. Attack-move both armies into his and enjoy the meal.
What units are you talking about? Drones: Split fast Zerglings: Try to get a good surround on the units, attack units while making them chase a single zergling. Move away low health zerglings. Roaches: Position them so they tank damage, focus fire. Hydras: Position them behind zerglings/roaches so they don't get attacked as easily. Focus fire units that are dealing the most damage against your army. Infestors: Lots of good stuff... fungal growth units that rely on mobility so that you can kill them more easily. Fungal growth low hit point units so they are easier to kill. Overlords: Spread creep. Mutalisks: Avoid any anti air, as mutalisks are fairly fragile. Take advantage of their mobility to flank units or attack the enemy's workers. Focus fire if you are trying to kill units. Banelings: Protect them by sending them in with zerglings, have them hit blobs of units or send them into a mineral line. They do most damage against light units like marines/zerglings/workers. Corruptors: Mostly useful for attacking capital air (carriers, battlecruisers) - focus fire and use the corruption ability on as many units as possible. Ultralisks: Use them to tank damage, try to attack bunches of units with them, include zerglings with them for distraction. Ultralisks do splash damage so can take out a large blob of units very quickly. Overseers: Corrupt (spell name?) the buildings that the enemy is using the most. Warpgates would be good structures to corrupt. Queens: The unit that can make or break any zerg player. Always always spawn larva as fast as possible. Ideally, you would be constantly spawning larva all game. Have extra queens for extra protection and spreading creep. Use transfusion on low hit point units and structures.. commonly used on other queens and on structures like spine crawlers. Creep tumors: Spread them like cancer.
