Preheat your grill or grill pan to 350°F. Then, if using an outdoor grill, add apple or cherry chips to the smokebox.
Cut zucchini in half lengthwise. Using a large spoon, scrape out the fleshy center and seeds leaving ¼ inch shell (reserve the flesh for the filling) — brush oil over the inside of each half, salt, and pepper. Place cut side down on a hot grill (350°F), grill six minutes, turn one quarter turn to create cross grill marks, continue grilling six more minutes before removing. Cover with foil to keep the grilled halves warm until filling.
Meanwhile, remove sausage from casings into the skillet, sprinkle with Italian sausage seasoning, add minced garlic, chop sausage, cooking over medium-low heat for 1-2 minutes until the meat is no longer pink. Remove from pan and set aside.
Roughly chop the reserved zucchini flesh from step one, then add the onion, pepper, and Italian seasoning blend to a bowl. Stir to combine.
Combine the mixed vegetables and tomatoes in the skillet over medium-high heat, cook about 10 minutes until the mixture has dried up and is no longer super moist. Add the cooked sausage and chopped parsley.
Fill the grilled zucchini halves with the hot vegetable and sausage filling, sprinkle with the grated mozzarella cheese.  Serve.
Footnotes: Just pop the prepared boats under a low broiler for 1-2 minutes before serving if you like extra melty cheese.Pro Tip for Grating CheeseTo grate cheese using a box grater or food processor, put blocks of softer cheese like Mozzarella or Colby in the freezer for a half-hour. It will make things much easier to slice and shred.