Place lentils and 2 cups water in a saucepan. Bring to a boil and cook 20-30 minutes, or until lentils are tender. Drain and set aside. Heat oil in a large pot; add onion and saute until soft. Add garlic, carrots, mushrooms, and zucchini; saute until zucchini starts to soften. Add walnuts, lentils, tomatoes, basil, oregano, ½ cup water and salt. Simmer, covered, for 15-20 minutes. Serve over pasta, topped with grated Parmesan. While sauce is simmering, bring a pot of water to a boil. Add noodles and cook until al dente. Drain and rinse. Serve with the sauce.