Preheat oven to 425 degrees, with racks in upper and lower thirds. Lightly coat two rimmed baking sheets with cooking spray. In a wide, shallow dish, mix together panko, Parmesan, Italian seasoning, cayenne, 3/4 teaspoon salt, and 1/4 teaspoon pepper. In a medium bowl, lightly beat egg whites.
Working with one at a time, dip zucchini wedges in egg whites, then breadcrumb mixture, pressing to adhere. Arrange on sheets in a single layer. Bake until coating is golden brown and crisp, 20 minutes, flipping zucchini and rotating sheets halfway through. Season to taste with salt and pepper; serve immediately.