In a large skillet, brown the meatballs in the oil. Add the sauce and carrots. Cover and simmer for about 2 minutes or until the meatballs are cooked through. Add the zucchini, onion, and sauce and stir until well coated. Bring to a boil and cook, covered, for about 1 minute. Adjust the seasoning. Serve with steamed rice or mashed potatoes.