Start by preheating your oven to 375°F (190°C). Slice the zucchini lengthwise into thin strips, about 1/8-inch thick. Sprinkle the slices with salt and lay them on a clean kitchen towel for about 30 minutes to sweat out excess moisture. After sweating, pat the zucchini dry with paper towels.
In a large mixing bowl, combine the ricotta cheese, egg, shredded mozzarella, Parmesan cheese, Italian seasoning, and season with salt and pepper. Mix well until fully combined.
In a 9x13 inch baking dish, spread a thin layer of marinara sauce on the bottom. Arrange a layer of zucchini slices on top, slightly overlapping them. Spread half of the cheese mixture over the zucchini, followed by a layer of marinara sauce. Repeat the layers, finishing with a layer of zucchini and marinara sauce on top.
Top the final layer with the remaining mozzarella and Parmesan cheese. Optionally, sprinkle fresh herbs like basil or oregano.
Cover the baking dish with aluminum foil and bake for 25 minutes. After 25 minutes, remove the foil and bake for an additional 15-20 minutes, or until the cheese is bubbly and golden brown.