Preheat the oven to 375F

Heat the oil in a large skillet over medium-high heat. Add the garlic and saute for 30 seconds. Add half the spinach and 1/2 the salt. Cook for about 3 minutes, until it is wilted. Add the rest of the spinach and cook an additional 3 minutes, until it is wilted. Transfer the spinach to a colander and drain out as much liquid as possible.

Add the zucchini to the saute pan and cook for 3 minutes. Add the zucchini to the colander and drain out as much liquid as possible.

In a small bowl, stir together the ricotta, egg yolks, nutmeg and the remaining salt.

In a 9×13 inch deep baking dish, layer 1 cup marinara, 1/2 the polenta slices, 1/2 the spinach/zucchini mixture, 1/2 the peppers, 1/2 the marinara sauce, 1/2 the ricotta, 1/2 the mozzarella, and 1/2 the parmesan. Repeat layering to use the remaining ingredients.

Cover with foil, and bake for 30 minutes. Remove the foil, and bake, uncovered, an additional 15-20 minutes, until heated through and the cheese is bubbly.

Remove from the oven and cool 10 minutes before serving.