Preheat oven to 375°F (190°C).
In a saucepan, heat olive oil over medium heat. Add garlic, zucchini, and mushrooms. Cook until tender.
In a mixing bowl, combine ricotta cheese, spinach, salt, pepper, and dried oregano.
Spread a thin layer of marinara sauce on the bottom of a baking dish. Place a layer of lasagna noodles on top.
Spread half of the ricotta mixture over the noodles. Add a layer of the cooked vegetables. Sprinkle with mozzarella and Parmesan cheese.
Repeat layers, ending with a layer of noodles and marinara sauce. Top with remaining mozzarella and Parmesan cheese.
Cover with foil and bake for 30 minutes. Remove foil and bake for an additional 15 minutes, until cheese is bubbly and golden.
Let lasagna rest for 10 minutes before serving.