If you know how to three-star the normal level, you'll know how to three-star here. But there is a different way to get high scores in this level.
High scores are based on destruction and luckiness. So keep trying to earn higher scores.
If you just want three-star, that'll be pretty easy as the normal version. Simply shoot the Lazer Bird directly above the tower, then destroy the horizontal wood blocks which are in the middle of the second stone tower which has two TNTs. After the TNTs explode, shoot the second bird over Hekto Porko and then tap the bottom-left of Hekto Porko's structure. He should fly there and Hekto Porko will be popped and you'll get 3 stars. But if you want high scores, there is an another way below.
In this strategy, we'll make the towers fall with a domino fashion and get incredibly high score. Shoot the Lazer Bird pass the first tower (counting from right to left). Then, tap the bottom-left of the first tower when he's flying between the first and the second tower. This should make the first tower fall on the second tower and make it explode, as well as damaging Hekto Porko along with his structure.