You’ll want a full group of 12 Guardians, 5 or 6 Devourers and a few Overlords for this attack. Leave some units stationed there until you can get 2 or 3 Sunken Colonies built to defend this base.
Once you have destroyed the southern Terran base bring in 3 Drones to gather gas and a few more for harvesting the minerals. To destroy the souther Terran base about 6 Guardians should be enough but you may want to bring some of the other units that you started with like the Ultralisk and Hydralisks to help out. This will give you a head start in destroying the base later and the Protoss won’t mount a defence if you don’t go past the hill. While you’re waiting you can send out the 2 Guardians that you started with to destroy the 3 Crystals and Protoss Cannons on the hill where the Matriarch is being kept. Start mutating Mutalisks and turn them into Guardians. You’ll want to take over the small Terran base to the south for the gas and minerals. You also have a small force of various units. You don’t need to worry about defending your base for this mission as it comes with Sunken Colonies already in place. Produce more Drones from the two Hatcheries and set them to work gathering minerals. Grab 3 Drones and set them to harvesting gas, the rest can gather minerals. You’ll need to move quickly for this mission because you only have 30 minutes to destroy all Protoss structures (25 minutes if you want to unlock the bonus mission). Destroy the Protoss Base Within 30 Minutes (25 Minutes to Unlock the Secret Mission)