Bad Piggies Flight in the Night Bonus Level 4-III (4-3) can be 3-starred in two runs, but it may be the most challenging level in the set. Put both powered wheels atop the contraption, blue firework on top, red firework on the bottom. The real trick here is to do a half-flip at the top of the level, so the powered wheels will be on the bottom when you drop into the middle level. Even still, the timing of using the last firework is tough and you will usually wreck trying to climb the last incline.
If you have a different strategy for completing this level feel free to leave a comment below.