This level is hard because:
Send Han high and far, shoot the wooden base of the central tower with his blaster. The black TNT should detonate from the falling debris, and Han can pop one (or both) of the well-guarded mynocks in the cave with a little luck. If necessary, send Luke along a similar trajectory, using the lightsaber to cut away the footing of the far tower. Either falling debris or a falling Luke should finish off the cave with your luck.
Send Han Solo High. Shoot the wooden base of the right tower. Cause the wheel fall down to all Mynock Pigs in the right side. Send Luke to destroy the base of the central tower. Cause the tower fall down to the black TNT.
See Video Walkthrough.