1. Preheat your oven to 375°F and lightly grease a 9×13-inch baking dish.

2. In a skillet, heat the olive oil over medium heat. Add the onion and garlic, and sauté until fragrant. Then, add the ground beef, season with salt, pepper, and Italian seasoning, and cook until browned. Stir in the marinara sauce to create a flavorful beef mixture.

3. Arrange a layer of sliced zucchini in the bottom of the prepared baking dish. Spread some of the beef mixture on top, and add small dollops of ricotta cheese if desired.

4. Continue layering the zucchini, beef mixture, and cheeses until all the ingredients are used up, finishing with a layer of mozzarella and Parmesan on top.

5. Cover the casserole with foil and bake for 20 minutes. Then, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden brown.

6. Garnish the Ground Beef Zucchini Casserole with fresh basil leaves and a sprinkle of red pepper flakes, if desired. Serve hot and enjoy the comforting flavors!