Stir the soup and milk in a small bowl and set aside. Spray a 13 x 9 x 2-inch shallow baking dish with the cooking spray.
Heat the butter in a 12-inch skillet over medium heat. Add the mushrooms, peppers, zucchini and onion and cook until they're tender.
Spread 1 cup soup mixture in the bottom of the prepared dish. Layer with 3 of the noodles, 1/3 of the vegetable mixture, 1 cup of the soup mixture and 1/2 cup of the cheese. Repeat the layers twice. Top with the remaining 3 noodles. Pour the remaining soup mixture over the noodles. Cover the baking dish.
Bake at 375°F. for 40 minutes. Uncover and sprinkle with the remaining cheese. Bake for 10 minutes or until it's hot and bubbling. Let the lasagna stand for 10 minutes.