Preheat the oven to 375°F (190°C).
Slice the zucchinis lengthwise into thin strips.
Sprinkle salt on the zucchini slices and let them sit for about 10 minutes to draw out moisture.
In a bowl, mix ricotta cheese, egg, Italian seasoning, salt, and pepper until well combined.
Spread a thin layer of marinara sauce at the bottom of a baking dish.
Layer zucchini strips on top of the sauce.
Add half of the ricotta mixture over the zucchini.
Sprinkle a layer of mozzarella cheese on top.
Repeat the layers: sauce, zucchini, ricotta, and mozzarella.
Finish with a final layer of zucchini, sauce, and the remaining mozzarella and Parmesan cheese on top.
Cover with foil and bake for 30 minutes.
Remove the foil and bake for an additional 10 minutes, or until the cheese is golden and bubbly.
Let it rest for 10 minutes before serving.