Preheat oven to 350°. Cook noodles according to package directions. Meanwhile, in a 6-qt. stockpot, cook beef, zucchini, onion and green pepper over medium heat until beef is no longer pink, breaking up beef into crumbles. Add garlic; cook 1 minute longer. Drain., Stir in pasta sauce, diced tomatoes, basil, flax, Italian seasoning and pepper; heat though. Drain noodles and rinse in cold water., In a small bowl, mix ricotta cheese, spinach, egg and vinegar. Spread 1 cup meat mixture into a 13x9-in. baking dish coated with cooking spray. Layer with three noodles, 2 cups meat mixture, 1-1/4 cups ricotta cheese mixture and 2/3 cup mozzarella cheese. Repeat layers. Top with remaining noodles, meat mixture and mozzarella cheese; sprinkle with Parmesan cheese., Bake, covered, 30 minutes. Bake, uncovered, 10-15 minutes longer or until cheese is melted. Let stand 10 minutes before serving.