Preheat oven to 350. Combine beef, onion, and garlic in a large skillet; cook over medium heat until browned, stirring frequently. Add marinara, tomatoes, and paste. Stir well. Bring to a boil. Let simmer 20 minutes.
Slice zucchini lengthwise into 1/4 inch thick slices. Add cheeses to a medium bowl. Stir to combine.
Pour 1 1/3 cups sauce in the bottom of a 13X9 baking dish. Top with a layer of zucchini. (Edges may slightly overlap.) Top with 1/2 the cheese. Repeat layers (sauce, zucchini, cheese).
Bake at 350 for 25 minutes. Let stand 10 min before cutting.