The meat sauce can be prepared the day before to cut the recipe time in half. Follow the instructions here.
Preheat the BBQ to 550°F (290°C). Meanwhile, cut the ends off of the zucchini and slice thinly lengthwise. Cook on each side for about 5 minutes on the BBQ. Set aside.
Preheat the oven to 400°F/200°C.
Meanwhile, in a 9x13 inch baking dish, spread a layer of the meat sauce on the bottom. Add a layer of sliced zucchini on top of the meat sauce. Spoon some of the meat sauce on top of the zucchini layer. Sprinkle a third of mozzarella cheese and pecorino cheese on top of the meat sauce. Add another layer of sliced zucchini and top with meat sauce, mozzarella and pecorino cheese. Add a final layer of sliced zucchini on top of the cheese layer. Add the final zucchini layer and cover with meat sauce.
Cover with foil and bake for 20 minutes. Remove the foil, sprinkle the remaining shredded mozzarella cheese and pecorino cheese on top of the meat sauce and bake for an additional 5-10 minutes, or until the cheese is melted.