In a skillet over medium heat, brown the sausage until no longer pink; drain. Cut sausage into 1/4 in. slices; return to the skillet to brown completely. Add zucchini and onion; cook and stir for 2 minutes. Stir in the tomatoes. Reduce heat; cover and simmer for 10-15 minutes or until the zucchini is tender. Serve over rice or pasta.