Preheat oven to 350 degrees. Either prepare your marinara sauce or purchase a 32 oz. jar. Take lasagna sheets out of the fridge to warm up. You'll need a 9 x 12 pan.
Prepare veggies by heating the olive oil in a large saucepan over medium heat. Add onion and garlic, cook for 3 min. Add diced tomatoes, zucchini, squash, mushrooms, salt, pepper, garlic powder, and oregano. Mix well and cover. Cook until veggies begin to soften, about 10-15 min. stirring often. Once cooked, remove from heat and stir in fresh basil and parsley. Set aside.
While veggies are cooking, mix all the cheeses, egg, salt, and pepper together in a large bowl. until smooth Set aside.
Begin layering the lasagna. Spoon in 1/2 cup of sauce onto the bottom of the pan. Add a layer of noodles, then top with half of the veggie mixture and half of the cheese mixture, top with 1 1/2 cup of sauce. Repeat for the second layer. On the final top layer of noodles, pour 1/2 cup of sauce and sprinkle 1/4 cup of mozzarella cheese evenly. Cover in foil and bake for 45 min. Remove when bubbly, remove foil and let rest for 10 min. before serving.