Prepare Oven: Arrange oven racks on middle rack and top rack. Preheat oven to 450 degrees F. Line a baking sheet with parchment paper.
Season Zucchini: To a mixing bowl, add sliced zucchini, 2 Tablespoons shredded Parmesan, oil, Italian seasoning, garlic powder, salt, and pepper. Gently stir zucchini slices with a spoon until slices are coated in seasoning mixture.
Top Zucchini With Parmesan: Transfer zucchini to prepared baking sheet and arrange in an even layer (do not overcrowd the baking sheet; use a second baking sheet, if necessary). Top zucchini with remaining 6 Tablespoons shredded Parmesan.
Bake: Transfer baking sheet to middle rack in oven and bake for 6-7 minutes.
Broil: Turn on oven broiler, transfer baking sheet to top rack and broil until cheese on top is golden and bubbly, about 2-4 minutes, watching carefully to avoid burning. Then, remove baking sheet from the oven.
Serve: Allow zucchini slices to briefly cool before serving.
