In a large skillet, cook beef and onion over medium heat until meat is no longer pink; drain. Stir in the spaghetti sauce, tomatoes, basil, oregano, fennel and garlic. Bring to a boil. Reduce heat; cover and simmer for 10 minutes.
Spread 1-1/2 cups meat sauce in a greased 13x9-in. baking dish. Top with three noodles. Spread 1-1/2 cups sauce to edges of noodles. Top with half of the zucchini, 1/2 cup ricotta cheese and 1/2 cup Asiago cheese. Repeat layers. Top with remaining noodles, sauce and Asiago cheese.
Cover and bake at 375° for 30 minutes. Uncover; bake 10-15 minutes longer or until bubbly. Let stand 5 minutes before cutting.