In a skillet, heat olive oil over medium-high heat and brown ground beef 10 minutes, breaking up beef as it crumbles, until it's completely cooked through. Drain fat then transfer browned ground beef, using a slotted spoon, to a mixing bowl. Season with salt and black pepper to taste. Cut zucchini in half lengthwise, and, using a spoon, scoop out the flesh, leaving about inch-thick boat. If zucchini is too tough to scoop out, boil it for a few minutes or soak it in cold water for 10 minutes first. In the mixing bowl, combine zucchini pulp, bread crumbs, garlic, black olives, spaghetti sauce, and cheese in the bowl with the cooked ground beef until all are fully incorporated. Taste and season with salt and black pepper to taste. Stuff each zucchini half with the stuffing mixture, packing it in pretty tightly. Cover baking dish with foil. 40-45 minutes. They should be knife-tender, but not so tender that they fall apart at the touch or are mushy. When they are done, remove from oven and remove foil. Season with a few grinds of black pepper if desired. Place oven rack 6 inches (15.2cm) from the broiler element, turn broiler on, and broil zucchini 5 minutes until the mozzarella is browned and bubbling. Remove zucchini from the oven and cool for at least 3-4 minutes. Enjoy this hearty dish on its own or with a side of rice or pasta.

Summary:
Preheat oven to 350F (175C). Cook the beef. Prepare the zucchini. Prepare the stuffing. Stuff the zucchini. Place the zucchini on a baking dish. Bake zucchini Sprinkle mozzarella cheese over each zucchini half. Broil zucchini 5 minutes. Serve.