Starcraft 2, Brutal difficulty walkthrough with commentary
Mission 5: Smash and Grab

In this one, you race the zerg to a waypoint past a hostile protoss base. There are 4 protoss relics to collect for research points. Watch the walkthrough for the locations. You have plenty of time; just make a big army of marines, medics, and marauders (new unit) and you will have no problems.