At the very start of the mission, deploy your MCV and begin to built some structures. While you're doing this shit, send all your combat units to attack the fat ass Emperor Worm. You'll lose some units, but if you use them right, you can beat this damn mission in less than 4 min. DON'T attack anyone else if they're fire at you; ignore them, just attack the worm. You can use this with the other two Houses.