Preheat oven to 375 degrees. Coat a 9 x 9-inch baking pan with cooking spray.
In a microwave-safe bowl, add onions and mushrooms. Cook in the microwave for 4 minutes. Drain liquid. Next, place zucchini in a microwave-safe bowl and cook in the microwave for about 3 minutes, until soft. Drain liquid.
Coat a large nonstick pan with cooking spray. Add ground turkey and garlic. Cook, breaking up the pieces until browned. Once browned, stir in 1 cup pasta sauce, cooked onions and mushrooms, Italian seasoning, and pepper. Mix well.
In a bowl, mix together the ricotta cheese and egg. Combine well.
To assemble lasagna: Spread ¾ cup pasta sauce on the bottom of baking pan. Add ½ of cooked zucchini. Spread ½ ricotta mixture over zucchini. Spread the entire turkey mixture over top of the ricotta. Add remaining zucchini over top of turkey. Add remaining ricotta. Spread remaining pasta sauce over the top of the ricotta. Sprinkle mozzarella cheese all over. Finally sprinkle top with Parmesan cheese.
Cover with foil and bake for 25 minutes.
Remove foil and let casserole sit for 15 minutes. Cut into 6 slices.
This casserole freezes great!