Heat a large nonstick skillet sprayed with cooking spray on medium-high heat. Add chicken; cover skillet with lid. Cook about 5 to 7 minute on each side or until chicken is done, adding onions and zucchini after 5 minute
Add the dressing, tomatoes and olives; cover. Cook on medium-low heat about 2 minute or until heated through.
Stir mixture. Top with cheese; cover. Cook 2 minute or until cheese is melted.