Preheat the oven to 375°F (190°C).

In a mixing bowl, combine the ricotta cheese, egg, oregano, garlic powder, salt, and pepper. Mix until well combined.

Spread a thin layer of marinara sauce on the bottom of a 9x13 inch baking dish.

Layer half of the zucchini slices over the sauce, followed by half of the ricotta mixture, half of the mozzarella cheese, and half of the marinara sauce.

Repeat the layers with the remaining zucchini, ricotta mixture, mozzarella, and marinara sauce.

Top with grated Parmesan cheese and drizzle with olive oil.

Cover the dish with aluminum foil and bake in the preheated oven for 30 minutes.

Remove the foil and bake for an additional 15-20 minutes, or until the cheese is bubbly and golden.

Let it cool for 10 minutes before slicing and serving.