This stage can be pretty tough if you do not know what to aim for. Aim low with your first launch. You want to kill all of the pigs on the right side with this shot.
Power Activation Point
Tap for the power up when you are about the middle as shown in the picture.
First Shot Result
You want to fly through the gap, while letting the second bird killing the majority of the pigs on the ground. The main bird continues to fly to destroy all of the pigs inside the right structure.
If you have killed all of the pigs like the picture, just finish up. However, if you did not kill the pig on the top platform, aim for the TNT bomb on the platform.
Second Power Activation Point
You do not really need to use power up with this shot.
Second Shot Result
After setting of the bomb, the pig on top gets killed immediately. The metal block and the metal chain drops down to pick out the left over pigs. Leaving you with the awesome three star mastery.