First of all, take the Heart in the bottom-left corner for two Magic Shots.
The real trick here is to use Leeper twice! First, take the heart and release it, then move down, and shoot it in a place where the egg can be pushed to rhe right (e.g. if you locate Lolo near the lower rocks, half-tile visible to Medusa, Leeper will pass to the left, Lolo can then move up and shoot Leeper on its way up). Pass above the egg and position Lolo half-visible to the right of Medusa. When Leeper arrives, shoot it and push the egg down, so to block Medusa's line of sight to the right. Wait for the egg to break and put Leeper to sleep.
Collect the two Hearts in the left half of the room for two more Magic Shots. Pay attention to Don Medusa and move right under Snakey, thus pushing the Emerald right just one tile.
Shoot Snakey once and push it up, collect the Heart to the left, run back and shoot the egg away before it cracks open, and get below the Emerald to the left. Push the left Emerald left and trap Don Medusa in the leftmost tile of his trajectory. Before Snakey reappears, push the middle Emerald on its location, and Snakey will reappear below the nearby Medusa (enemy hole).
Push the middle Emerald between Medusa and the last Heart, and grab the latter.
Push the rightmost Emerald down next to Medusa, collect the gem, and leave from the staircase.
