Preheat the oven to 375°F (190°C).
In a large pot, cook lasagna noodles according to package instructions until al dente. Drain and set aside.
In a skillet, heat olive oil over medium heat. Add chopped onion and garlic; sauté until translucent.
Add zucchini, bell pepper, and mushrooms to the skillet; cook for about 5-7 minutes until they are tender. Stir in spinach and cook until wilted. Season with salt, pepper, and Italian herbs.
In a mixing bowl, combine ricotta and half of the mozzarella cheese. Add a pinch of salt and pepper.
To assemble the lasagna, spread a layer of white sauce on the bottom of the baking dish. Place 3 lasagna noodles over the sauce. Spread half of the ricotta mixture, half of the veggie mix, and a layer of white sauce on top. Repeat the layers, ending with a final layer of noodles topped with remaining white sauce.
Sprinkle the remaining mozzarella and Parmesan cheese on top.
Cover the dish with aluminum foil and bake for 25 minutes. Remove the foil and bake for an additional 20 minutes, or until the top is bubbly and golden.
Let the lasagna sit for about 10 minutes before slicing and serving.