Preheat oven to 400 degrees Fahrenheit. Prepare muffin tins with liners or grease.

In a large bowl, combine flour, sugar, baking powder, baking soda, salt, and orange zest. Stir in the dark chocolate chips.

In a medium bowl, whisk together butter, orange juice, vanilla extract, and eggs. Gently add to the dry ingredients just until combined. Be careful not to overmix.

Fill the batter to the rim of each prepared muffin tin. Bake in preheated oven until the tops are golden and toothpick inserted in the center comes out dry (minus the chocolate), 20-25 minutes.

Let cool in pan 5 minutes before removing to wire rack.