Slice the zucchini into 1/4 inch rounds, sprinkle with salt and let sit for 20 minutes.

Heat olive oil in a large skillet and sauté diced onion and minced garlic until softened.

Add spinach and cook until wilted, then drain excess liquid.

Whisk together eggs and heavy cream in a mixing bowl, then add oregano, dill, and crumbled feta.

Preheat oven to 375°F (190°C) and grease a 9x13 inch baking dish.

Layer half of the zucchini in the dish, followed by the spinach mixture and half of the custard. Repeat the layers.

Top with shredded mozzarella and optional grated parmesan.

Bake for 35 to 45 minutes or until cheese is bubbly and golden brown.

Let cool for 10 minutes before serving.