HEAT dressing in large skillet on medium-high heat. Add onions, garlic and seasoning; cook 3 min., stirring occasionally. Add zucchini; cook and stir 4 to 5 min. or until crisp-tender.
STIR in snow peas and tomatoes; cook 2 to 3 min. or until heated through, stirring occasionally.
SPRINKLE with cheese; cover. Remove from heat. Let stand 1 min.