Core and cut each zucchini into 3 pieces. In a bowl mix together Mortadella, chicken, ricotta, Parmesan, egg, parsley, garlic, nutmeg, salt, and pepper. Stuff the zucchini with the filling and put bread crumbs on both ends of the zucchini.
Arrange the zucchini in a baking pan and sprinkle with celery, carrots, and onions. Crush the peeled tomatoes with your hands and place over the zucchini. Drizzle with olive oil. Cover with aluminum foil and bake at 350 degrees for 45 minutes. Uncover and bake for an additional 15 minutes.