Send the first Leia up and over the first two towers and use her tractor beam on the roof of the far right structure. With a bit luck, one of the pieces of the roof will fall down the far right gap and detonate the TNT. The resulting chain reaction should finish off the level.
Send Leia up and over the first two towers. Use her tractor beam on the roof between two towers. With a bit luck, this should kill all the pigs on the two towers, Viper Probe Droid, and all snowtroopers. Moreover, it cause to detonate the TNT and the iron wheel will crush the rightmost ice block.
See Video Walkthrough.