Remove and discard casings from sausage. Cook in large skillet, stirring until sausage crumbles and is no longer pink. Drain. Add onion, zucchini, salt and pepper to skillet. Saute 4 min or until vegetables are tender, stir in peppers. Drain and cool. Spread 4 c bread crumbs in lightly greased 9x13. Top with half sausage mix and half cheese. Repeat. Whisk together eggs and milk, pour over bread. Cover and chill 8 hours. Bake, covered, at 325 degrees for 1 hour or until bubbly and hot.