01 - Preheat the oven to 400°F and line a baking dish with parchment paper or lightly grease it.
02 - Slice zucchini lengthwise and scoop out the center flesh with a spoon, leaving a 1/2-inch thick shell; finely chop the reserved flesh.
03 - Heat olive oil in a large skillet over medium heat. Add diced onion and cook until softened, about 2 to 3 minutes.
04 - Add minced garlic and diced red bell pepper to the skillet; cook for 2 minutes. Stir in chopped zucchini flesh and sauté for another 2 minutes.
05 - Add ground chicken, breaking it apart as it cooks, and sauté until no longer pink, approximately 5 to 6 minutes.
06 - Stir in tomato sauce, dried Italian herbs, salt, and black pepper. Simmer the mixture for 3 to 4 minutes until slightly thickened, then remove from heat and allow to cool briefly.
07 - Arrange zucchini boats evenly in the prepared baking dish and spoon the chicken mixture into each shell.
08 - Sprinkle shredded mozzarella and grated Parmesan evenly over the filled zucchini boats.
09 - Bake for 20 to 25 minutes until zucchini is tender and cheese is golden and bubbly.
10 - Remove from oven, garnish with freshly chopped parsley, and serve.