Preheat your oven to 375°F (190°C). Cook lasagna noodles until al dente, drain, and set aside in olive oil.

In a large skillet, heat olive oil over medium heat. Add chopped onion and cook for 3-4 minutes until translucent. Stir in minced garlic and sauté for another minute.

Toss in zucchini, red and yellow bell peppers, and mushrooms into the skillet. Sauté for 5-7 minutes until vegetables are tender and slightly browned.

Add fresh spinach to the skillet and stir until wilted (about 2 minutes). Pour in marinara sauce, sprinkle basil and oregano, and let simmer for 5 minutes.

In a mixing bowl, combine ricotta cheese, egg, salt, and pepper. Stir until smooth and creamy.

In a baking dish, spread a thin layer of vegetable sauce on the bottom. Place 3 cooked lasagna noodles on top.

Spread half of the ricotta mixture over the noodles, followed by half of the vegetable sauce. Sprinkle 1 cup of mozzarella cheese on top.

Repeat layering with another 3 noodles, the rest of the ricotta mixture, the remaining vegetable sauce, and another cup of mozzarella.

Finish with the final 3 noodles, cover with the last of the marinara sauce, and sprinkle remaining mozzarella and parmesan cheese on top.

Cover with foil and bake for 25 minutes. Remove foil and bake for another 15 minutes until cheese is bubbly and golden brown.

Allow lasagna to cool for about 10 minutes before slicing to ensure neat servings.