Preheat the oven to 350℉. Line a muffin pan with 9 parchment muffin liners.
In a large mixing bowl, combine the flour, sugar, baking powder, baking soda, salt, and cocoa powder. Stir to combine.
Add the milk, egg, oil, and shredded zucchini. Stir until all of the ingredients are thoroughly incorporated. Stir in the chocolate chips.
Using a 1/2 cup measure, scoop the batter into the muffin liners. Fill each liner a little over 3/4 full.
Bake for 20-25 minutes. The muffins should bounce back when gently pressed and a toothpick inserted into the center of a muffin should come out with only a few moist crumbs.
Allow the muffins to cool in the pan for 10-15 minutes before transferring them to a cooling rack to cool completely. These muffins can be enjoyed warm, at room temperature, or toasted!