Return to the Batmobile and carefully approach the Cobra tank. Just as before, you must not cross the tank's path, so keep a careful eye on the mini-map and, if necessary, drive into back alleys. Your goal is to get exactly behind the Cobra tank. Approach it so to start the aiming process targeted at its rear (as shown in the above picture) and when it is ready use the 60mm cannon. A single hit should destroy the enemy machine.