Prepare the Oven and Baking Dish: Preheat the oven to 400°F and lightly coat a 9×13-inch baking dish with cooking spray.
Cook the Chicken: Place a large non-stick skillet over medium-high heat, add the ground chicken, and break it apart with a spoon. Season with the salt and black pepper, then cook for 8–10 minutes, stirring occasionally and breaking the chicken into small chunks, until it is cooked through. Add the Garlic: Lower the skillet heat to low, add the minced garlic to the cooked chicken, and cook for 1 minute, stirring frequently.
Stir in the Pasta Sauce: Add the pasta sauce to the chicken mixture and cook for 3 minutes, stirring occasionally so the ingredients are evenly combined.
Prepare the Zucchini: While the chicken mixture cooks, slice each zucchini in half lengthwise.Use a spoon to scoop out the seeds and center from each half, leaving about ¼ inch of zucchini to form the boat. Arrange the Zucchini: Place the prepared zucchini halves cut-side up in the greased baking dish.
Fill the Zucchini Boats: Spoon the chicken mixture evenly into the zucchini boats, pressing the filling gently into the zucchini with the back of the spoon.
Add the Cheese: Sprinkle the grated Parmesan evenly over the filled zucchini, followed by the shredded mozzarella.
Bake the Zucchini Boats: Cover the baking dish with foil and bake at 400°F for 35 minutes.
Finish and Serve: Remove the baked zucchini boats from the oven, sprinkle them with sliced fresh basil if using, and serve hot.