Preheat oven to 400. Spray 18 holes of two regular sized muffin tins with cooking spray. Or line with foil liners for easier cleanup and then spray.
Stir together meat, grated zucchini, egg, grated cheese, garlic, onion, and salt. Divide the meat between the holes of the prepared muffin tins. Press one cube of mozzarella into each meatloaf. Spoon a little sauce on each.
Bake for 30-35 minutes until cooked through. Serve with additional sauce if desired.