Preheat the oven to 450°F.
Combine bread crumbs, Parmesan, salt, and garlic powder in a small bowl. Whisk the egg in a second bowl and place the flour in a third bowl.
Make an assembly line with the bowls. Dip the zucchini circles first into the flour, then the egg, and finally the bread-crumb mixture, coating them evenly.
Place on a baking rack set over a baking sheet and spray with oil. Pop into the oven for 20 minutes, or until bread crumbs are golden. Serve with marinara sauce if desired.