If I may please ask grovelling humbly --- can someone help me (an extremely mediocre Zerg player) with any sort of strategy to win a 4v4 at the "Harder" level?

Any help will be valued.

I admit it, I like getting achievements

I have it for Terran and Protoss. Zerg is just a little beyond me I got a win with Zerg on the "Hard" level in 1v1 but when it comes to the 4v4 thing against AI, something goes pear-shape.