Preheat the oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners or grease the cups.
In a medium bowl, whisk together the all-purpose flour, unsweetened cocoa powder, baking powder, baking soda, and salt until well combined.
In a large bowl, beat the granulated sugar, light brown sugar, and eggs together until smooth and creamy.
Add the vegetable oil and vanilla extract to the egg mixture and mix until fully incorporated.
Gradually add the dry ingredients to the wet ingredients, stirring gently until just combined. Do not overmix.
Fold in the grated zucchini and mini chocolate chips until evenly distributed throughout the batter.
Divide the batter evenly among the 12 muffin cups, filling each about 3/4 full.
Bake for 18 to 20 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 5 minutes.
Transfer the muffins to a wire rack to cool completely before serving.