Preheat the air fryer: Preheat the air fryer to 400°F (205°C) for about 3 minutes. If your air fryer does not require preheating, you can begin with the zucchini immediately, but the first batch may need an extra minute or two.

Cut the zucchini evenly: Trim both ends of the zucchini and cut it into 1/2-inch (1.3 cm) thick half-moons. Try to keep the pieces similar in size so they finish cooking at the same time.

Season the zucchini: Place the zucchini in a large bowl. Add the olive oil, garlic powder, Italian seasoning, kosher salt, and black pepper. Toss until the pieces are lightly and evenly coated.

Add the Parmesan: Sprinkle the Parmesan over the seasoned zucchini and toss gently until the cheese is distributed over the pieces. Avoid pressing the zucchini together, which can encourage moisture to collect.

Arrange in the basket: Place the zucchini in the air-fryer basket in a single layer. Leave a little space between pieces when possible. If the basket is crowded, cook in two batches.

Air fry: Cook at 400°F (205°C) for 5 minutes. Shake the basket or turn the zucchini with tongs, then continue cooking for another 4 to 5 minutes.

Check for doneness: The zucchini is ready when the centers are tender when pierced with a fork and the edges are lightly browned. If you prefer more browning, continue cooking for 1 to 2 minutes, checking frequently so the Parmesan does not burn.

Garnish and serve: Transfer the zucchini to a serving dish and sprinkle with the optional fresh parsley. Serve immediately while the edges are at their crispest.