Although you can kill all the pigs with just a single shot, it is OK if you use a second shot to finish them off.
Launch the princess leia with the intention of hitting the X marked target in the picture.
Power Activation Point
Activate your pulling power any time during mid flight. Your purpose is to set off the flying pig and the bomb.
First Shot Result
After the bomb sets off, it pushes the blocks to the right which knocks down the right tower. If you cannot get it to work, having a second shot may still get you the three star mastery.