In a saucepan, combine the spaghetti sauce, tomato paste, mushrooms and oil. Simmer, uncovered, for 20 minutes. In a bowl, combine the next nine ingredients. In a greased 13x9-in. baking dish, layer half of the noodles and cheese mixture. Top with 2-1/2 cups of zucchini. Layer with a third of the spaghetti sauce and half of the mozzarella. Repeat layers of noodles, cheese mixture and sauce. Top with tomato slices and remaining sauce and mozzarella. Cover and bake at 350° for 35-40 minutes. Uncover and bake 10 minutes longer. Sprinkle with remaining zucchini. Let stand for 20 minutes before cutting.