1. Preheat oven to 450˚F. Generously spray inside of 5 1/2- or 6-quart Dutch oven with cooking spray.
2. Spread pasta in even layer in bottom of pot. Add enough water to tomato liquid to make 1 cup. Stir liquid into pasta with olive oil. Toss tomatoes with basil in separate bowl; season with salt and pepper. Spread over pasta. Top with half of zucchini rounds.
3. Combine ricotta, garlic, red pepper flakes, nutmeg, and salt in small bowl. Spread over zucchini. Layer mushrooms and remaining zucchini over ricotta mixture. Cover pot, and bake 53 minutes, or about 3 minutes after aroma wafts from oven.