Preheat the oven to 350°F.
Line a muffin tin with liners or lightly spray non-stick cooking spray. Set aside.
In a bowl, whisk together flour, cocoa powder, baking powder, baking soda and salt until well combined.
In another bowl, whisk together the oil, milk, eggs, vanilla, sugar, and brown sugar until smooth and well combined.
Stir in the grated zucchini to the wet mixture.
Add the wet mixture to the dry ingredients and stir until just combined. Don't over mix the batter or you will end up with very dense muffins.
Fold in the chocolate chips.
Fill the muffin tin until the cups are ¾ full and bake for about 20 minutes or until a toothpick comes out clean.
Cool for 5 minutes. Then remove the muffins to a wire rack to complete the cooling process.
The muffins are good for 3-5 days if stored in an airtight container.