Preheat oven to 425º F and line a rimmed baking sheet with parchment paper. Arrange zucchini slices on the parchment paper and spray lightly with cooking spray. Mix together Parmesan, parsley, black pepper, and salt. Sprinkle with Parmesan mixture. Bake for until cheese has melted and zucchini slices have become crisp, but not burned, about 30 minutes.