Cook and stir the ground beef in a skillet over medium heat until the meat is browned, breaking the beef up into crumbles as it cooks, about 10 minutes. Drain off excess fat, and transfer the beef into a mixing bowl. Slice the zucchini in half the long way, and use a spoon to scoop out the flesh, leaving a 1/2-inch thick shell all around the zucchini. Chop the scooped-out zucchini flesh, and add to mixing bowl. Stir in the bread crumbs, garlic, tomato sauce, almonds, olives, and Parmiggiano; mix the stuffing well. Lightly stuff both halves of the zucchini with the meat mixture. Place the zucchini halves into a baking dish, and cover tightly with foil.
Bake in the preheated oven for 45 minutes, remove from oven, and remove the foil. Add some sliced mozzarella cheese over each zucchini half. Move an oven rack to within 6 inches of the oven broiler's heat source, turn on the broiler, and broil the zucchini until the mozzarella cheese is browned and bubbling, about 5 minutes