Preheat the oven to 400˚F (200˚C). Line a baking sheet with parchment paper.
Cut the zucchini into ⅛- to ¼-inch (3- to 6-mm) slices. Arrange on the baking sheet, ensuring the slices aren't overlapping, otherwise they won't dry out properly. Brush the slices with olive oil, then season with salt, pepper, and garlic powder. Flip the slices over and repeat.
Bake for 25-35 minutes, flipping halfway, until golden brown. Let cool to room temperature. The zucchini will continue to get crispier as they cool.