Cut zucchini in half lengthwise, leaving stems intact. Carefully remove pulp, leaving 1/4-inch-thick shells. Dice pulp, and set aside; reserve shells.
Coat a nonstick skillet with cooking spray; place over medium-high heat until hot. Add zucchini pulp, onion, and garlic; saute 5 minutes. Transfer zucchini mixture to a medium bowl, and set aside.
Combine turkey and ham in skillet; cook over medium heat until turkey is browned, stirring until it crumbles. Combine turkey mixture, zucchini mixture, breadcrumbs, basil, peppers, and 1 teaspoon cheese, stirring well. Spoon turkey mixture evenly into reserved zucchini shells. Spoon spaghetti sauce into bottom of an 8-inch square baking dish; place stuffed zucchini shells over sauce. Sprinkle remaining cheese evenly over zucchini shells. Cover and bake at 350° for 30 minutes. Uncover and bake an additional 20 minutes.