In a shallow dish, stir together cornflakes cereal, cheese-flavored snack crackers, Parmesan cheese, garlic powder and cayenne pepper (if desired).
In another small bowl, stir together egg whites and water. Dip zucchini, cauliflower and broccoli into egg mixture.
Roll in crumb mixture, gently pressing crumbs onto vegetables. Place on baking sheet coated with nonstick spray.
Bake at 400°F for 8 to 10 minutes or until vegetables are crisp-tender.
Meanwhile, in a small microwave-safe bowl, heat pizza sauce on high for 30 seconds to 1minute or until heated through. Serve as dipping sauce with warm vegetables