Trim stems from zucchini and slice lengthwise. Scoop out seeds and put in bowl. Mix seeds with sausage, garlic, bread crumbs, and parmesan cheese. Stuff squash with sausage mixture and place in 9x13 inch baking pan. Pour sauce over squash and cover pan with foil.
Bake in preheated oven for 45 minutes, or until sausage is cooked. Remove foil and cover with mozzarella cheese. Cook until cheese is melted.