Fire a Yellow Bird directly at the Medium Pig next to the ice pillar. If done right, the Medium Pig will be killed and the pillar will topple. The corpse of the Yellow Bird should hit the Small Pig and kill it. Now, with precise aiming, launch it. When it's under the stone pillar and wood pillar at the same time, fire the egg. This should destroy the pillars and finish the pigs if aimed right.