Preheat air fryer to 400°. Coarsely grate zucchini, potato and onion. Place grated vegetables on a double thickness of cheesecloth or a clean tea towel; bring up corners and squeeze out any liquid. Transfer to a large bowl; stir in the egg, flour, Parmesan, garlic powder, onion powder, parsley, salt and pepper. Form mixture into 1/4-cup patties., In batches, place patties in a single layer onto greased tray in air-fryer basket. Cook until lightly browned, 15-20 minutes. Serve with sauce if desired., Oven method : Preheat oven to 400°. Place fritters on a parchment-lined baking sheet. Bake until golden brown, 15-20 minutes.