Preheat oven to 375°. In large skillet, cook and crumble beef with onion over medium-high heat until meat is no longer pink, 5-7 minutes. Stir in seasonings and tomato sauce. Bring to a boil; simmer, uncovered, 5 minutes. In a bowl, mix egg and cottage cheese., Trim ends of zucchini; cut lengthwise into 1/4-in.-thick slices. Toss zucchini with the flour. Layer half the slices in a greased 13x9-in. baking dish. Top with cottage cheese mixture and half the meat sauce. Add remaining zucchini slices; sprinkle with any remaining flour. Spread with remaining meat sauce; sprinkle with 1 cup mozzarella cheese., Bake, uncovered, until heated through, about 40 minutes. If desired, sprinkle with additional cheese. Let stand 10 minutes before serving.