Remove casings from sausage, if present. In a large skillet cook sausage and onion until meat is brown, breaking up meat during cooking. Drain fat. Stir in spaghetti sauce and water. Bring to boiling. Stir in noodles and zucchini. Return to boiling; reduce heat. Simmer, covered, about 12 minutes or until noodles are tender, stirring occasionally.
Meanwhile, in a small bowl stir together ricotta cheese, Parmesan cheese, and parsley. Using a spoon, drop cheese mixture into 6 mounds on top of sausage mixture. Sprinkle the mounds with mozzarella cheese.
Cook, covered, over low heat for 4 to 5 minutes or until cheese mixture is heated through. Let stand for 10 minutes before serving. Makes 6 servings.