Preheat oven to 400°F. Line a muffin tin with paper liners and lightly spray the inside of the liners with cooking spray.

In a large mixing bowl, whisk together the dry ingredients (flour, cocoa powder, baking powder, and salt) until evenly combined.

Shred the zucchini, then place the shredded zucchini in a clean kitchen towel or cheesecloth and squeeze out as much excess liquid as you can. Set the drained zucchini aside.

In a medium mixing bowl, whisk together the melted coconut oil, brown sugar, vanilla extract, eggs, and milk until the mixture is smooth and uniform.

Add the wet mixture, the drained shredded zucchini, and the mini chocolate chips to the dry ingredients. Stir gently with a spatula or spoon just until everything is combined — do not overmix.

Spoon or pour the batter evenly into the prepared muffin cups, filling each about three-quarters full.

Bake for 20–22 minutes, or until a toothpick inserted into the center of a muffin comes out clean or with a few moist crumbs.

Remove the muffins from the oven and let them cool in the tin for a few minutes, then transfer the muffins to a wire rack to cool further before serving.