Preheat oven to 425 degrees F. Line a rimmed baking sheet with parchment paper and coat it with olive oil spray.
Slice the zucchini into 1/8-inch-thick rounds. Arrange the slices on a platter or a tray and sprinkle with 1 teaspoon kosher salt. Place the salted zucchini in a colander and let stand 30 minutes at room temperature. This should draw water out of the zucchini. After 30 minutes rinse, then dry the zucchini slices using paper towels.
Arrange the zucchini slices in a single layer on the prepared baking sheet. Spray them with olive oil. Bake for 15 minutes.
Remove the baking sheet from the oven. Turn each slice to the other side. Spray with more olive oil and sprinkle with the garlic powder, the remaining 1/4 teaspoon of kosher salt, black pepper, and Parmesan.
Return to the oven, rotating the baking sheet, and continue baking until the zucchini slices are browned and crisp, about 15 more minutes.