Clear out the path with your first shot. You will have to destroy all of the ice blocks and possibly the single floating green block shown in the picture.
Power Activation Point
Activate your power where you can deal the most damage to the floating blocks.
First Shot Result
Aim for the leg of the building to the right, your goal is to drop the pig so that it swings.
Second Power Activation Point
Activate the power so destroy the supporting block.
Second Shot Result
The pig swings to set off the bomb. All the pigs die and you now have the three star mastery.