I'm lazy so i'll skip the boring part. Build a dron yadayadayada. Then you build 50 Mutalisk. Make 12 devourers and 12 guardians. Make sure you teched carapace and air attacks. Then make about 24 Ultralisk. You should have made another 50 mutalisk by now. Again do the 12 devourer and 12 guardian change. When that is done find a weak spot of the guys base and attack it with your guardians. Bring your devourers to protect them from other flyers. If he is sending a swarm of people to attack the flyers, then send your ultralisk. Send about 12. Then make a couple more. Keep sending fleets to make up for the guys you lost. If the enemy is terran then you might want to send the ultralisk to destroy turrets. If he is protoss you should clear a path from the photon cannons for the ultalisk to get in. Hope that works.

CreepColony's Opinion: This would require TONS of resources, so obviously a $$$ map strategy.