To get the three star for this stage, you will have to kill the pigs in one shot. Launch your princess bird towards the upper left platform. The angle for this shot does not have to be exact.
Power Activation Point
Activate the pulling power toward the block shown in the picture.
First Shot Result
You want the pieces to fall in both directions which get blown by the wind blower down below. The falling pieces kill the pigs and you will end up with the three stars mastery.