At the beginning of the mission just shoot down enemy choppers and planes and aim at the underbelly point of Joker's robot (picture) - they will be marked.
When you land at the robot use Batman's hook on the orange point on enemy's flying machine (picture) and eliminate the pilot. Use bricks to build platform with power suit.
Now aim at three silver bricks on the left robot's "shoulder-blade" (picture). When the gold plate will show up destroy it with Superman's laser and pull the handle. Do the same with right "shoulder-blade" and the mission will end.