First send Luke low into the bottom of the first tower toppling it to the left and popping those two pigs. Next send Chewie into the blocks on the nest platform. Finally send Obi-wan into the bottom platform but have him push upward hopefully bouncing a block off the one of the floating metal bars and into the Darth Vader, cause everything that he lift will fall to crush everything.
Darth Vader is introduced in this level.
See Video Walkthrough.