To successfully pass the mission, disable both tanks. To earn a commendation, suffer 75% or less damage on the police cruiser and 50% or less damage on APC. Quickly get to the tanks location on the map and start firing on it with your assault rifle. As soon as you are authorized to use it, fire on the tank with your standard police issue LAW rocket launcher. Then get in the APC and track down the other tank. In this vehicle you'll have a rapid-fire cannon so you should be able to make short work of the enemy tank.