Crumble ground beef into 16-oz casserole [1-qt casserole].
Cover loosely and microwave on high (550 watts) until very little pink remains, 1 to 1 1/4 min [1 1/2 to 2 min]; break up and drain.
Stir in zucchini and onion.
Mix chili sauce, green pepper, brown sugar, chili powder, salt and pepper; spread over beef mixture.
Cover loosely and microwave until vegetables are crisp-tender, 1 1/2 to 2 min [3 to 4 min].
Sprinkle with cheese.