Preheat the oven to 350 degrees. Line a baking sheet with parchment or foil, then coat with cooking spray.
Slice the zucchini into thick slices. Toss the zucchini coins with a drizzle of olive oil, sea salt, and freshly cracked pepper to taste, until evenly coated.
Place the coins on the baking sheet, then spoon a bit of marinara on top, followed by Parmesan cheese and a few panko crumbs.
Place in the oven and bake for 15-20 minutes, or until the zucchini is just tender and the panko is golden brown.