HEAT large nonstick skillet on medium-high heat. Add chicken; cover. Cook 5 to 7 min. on each side or until chicken is done (170ºF). Transfer to platter; cover to keep warm.

ADD dressing, zucchini and onions to skillet; cook on medium heat 4 min. or until vegetables are crisp-tender, stirring occasionally. Stir in tomatoes and snow peas; cook 1 to 2 min. or until heated through.

TOP chicken with vegetable mixture and cheese.