Step 1

Preheat oven to 375°F. Generously coat a 9-by-13-inch baking dish with cooking spray.

Step 2

Heat 2 tablespoons oil in a large skillet over medium-high heat. Add mushrooms, garlic, salt and pepper and cook, stirring occasionally, until the mushrooms are tender and starting to brown, 6 to 8 minutes. Transfer to a small bowl.

Step 3

Heat the remaining 1 tablespoon oil in the pan and add half the spinach. Cook, stirring frequently, until wilted, about 3 minutes. Add the remaining spinach by the handful and cook until it's all wilted, about 2 minutes more. Press the spinach to the side of the pan, squeezing out as much water as possible, and cook until the water is evaporated, 2 to 3 minutes more. Remove from heat.

Step 4

Mix egg, ricotta, 1 cup mozzarella and 1/2 cup Parmesan in a medium bowl. Combine the remaining 1/2 cup each mozzarella and Parmesan in a small bowl. Spread 1 cup sauce in the prepared baking dish and top with a layer of 3 noodles. Spread 1 cup of the ricotta mixture over the noodles and top with the mushrooms. Spread the spinach over the mushrooms and top with another 1 cup sauce. Layer on the remaining 3 noodles, followed by the remaining ricotta mixture. Layer zucchini on top, shingling if necessary, and spread the remaining sauce over the zucchini. Top with the reserved mozzarella mixture.

Step 5

Bake the lasagna until bubbly and the cheese is beginning to brown, about 45 minutes. Let cool for at least 10 minutes before slicing. Garnish with basil and/or parsley, if desired.