Cook penne to desired doneness as directed on package, adding zucchini and bell pepper during last 4 minutes of cooking time. Drain; cover to keep warm.
Meanwhile, melt margarine in large nonstick skillet over medium heat. Add onion and garlic; cook and stir 4 to 6 minutes or until onion is tender.
Add spinach and tomatoes; cook and stir 1 to 2 minutes or until spinach is wilted. Add cream, sherry, mustard and salt; mix well. Cook 10 to 15 minutes or until slightly thickened, stirring occasionally.
To serve, arrange cooked penne and vegetables on serving plate; top with cream sauce. Sprinkle with Parmesan cheese.