This level is interesting, in that you cause it to rotate 90 degrees every time you hit a P Switch. You can essentially collect the Green Stars out of order, as there’s always going to be a P Switch within reach. Just be careful about the enemies and you should be fine.
Green Star #1 and #2
Hit the first P Switch you start next to, then drop down, slip past the baddie, and grab the first Green Star. Then you can drop down to the lower level and collect another star. Make your way to the P Switch near the four Fizzlits on the ground level.
Green Star #3
Drop back down to the ground level, and make the walk around toward the third star. Hit the nearby P Switch when you’re done.
Green Star #4
You’ll have to rotate the camera around until you can see the fourth star, which is protected by two more baddies. Wait for them to give you a chance to slip past them, grab the star, and run for the next P Switch.
Green Star #5
Hitting this P Switch drops you right on top of a baddie next to the last Green Star. Time the rotation so that you fall on the enemy while he’s not electrified, then collect the star.