Preheat the oven to 375°F. In a large skillet, heat olive oil over medium heat. Add the diced onion and cook until translucent, about 5 minutes. Stir in the minced garlic and cook for an additional minute.

Add the zucchini, bell pepper, and mushrooms to the skillet. Sauté for about 5-7 minutes until the vegetables are tender. Stir in the fresh spinach, oregano, basil, salt, and pepper. Cook until the spinach wilts, then remove from heat.

In a mixing bowl, combine ricotta cheese, egg, and 1 cup of mozzarella cheese. Mix until smooth and well combined.

In a 9x13-inch baking dish, spread a thin layer of alfredo sauce on the bottom. Place three lasagna noodles over the sauce.

Spread half of the ricotta mixture over the noodles, followed by half of the sautéed vegetable mixture. Add another layer of alfredo sauce and sprinkle with 1/3 of the remaining mozzarella and 1/3 of the Parmesan cheese.

Repeat the layering process with three more noodles, the remaining ricotta mixture, the remaining vegetables, more alfredo sauce, and another 1/3 of the mozzarella and Parmesan cheeses.

Top with the final three lasagna noodles, the remaining alfredo sauce, and the rest of the mozzarella and Parmesan cheeses.

Cover the baking dish with aluminum foil and bake for 25 minutes. Remove the foil and bake for an additional 15-20 minutes, or until the cheese is bubbly and golden brown.

Let the lasagna cool for 10 minutes before slicing and serving.