You can get three star mastery even if you use two shots given that you have broken enough items. Your first shot need to aim right between the bomb and the platform. The key is to trigger all three bombs with your first shot for maximum damage.
Your goal for the first shot is to destroy all the pigs except for the ones hanging. However, it is possible to kill everything with just one single shot.
Power Activation Point
Activate your power when you can destroy both of the bombs.
First Shot Result
All the pigs are destroyed. If there are any pigs still hanging off the ceiling, use your second shot to finish them off. Remember to aim and hit for such a way that you can earn some additional points.
Once all the pigs are dead and your score high enough, you will then earn the three star mastery.