Whisk together first 5 ingredients in a large bowl. Combine buttermilk, milk, egg, and butter in a separate bowl; add to flour mixture, and whisk just until blended. Add 1 tablespoon orange zest and 1/2 cup semisweet chocolate chips to batter, and fold in gently. Transfer to a large measuring cup, and let stand 10 minutes.
Pour 3 to 4 tablespoons of batter onto a hot, lightly greased griddle or nonstick pan. Cook until pancakes are covered with bubbles and edges turn brown. Turn and cook other side 2 minutes or until golden brown. Serve with your favorite maple syrup.