Preheat the oven to 350F. Line a 12 cup muffin tin with liners. Set aside.
In a medium mixing bowl, add the dry ingredients (flour, cocoa powder, baking powder, baking soda and salt) and whisk well until its not lumpy.
Add the brown sugar and white granulated sugar and whisk into the dry ingredients.
Add the grated and drained zucchini, oil, and milk, mixing gently until combined and lastly stir in the chocolate chips.
Divide the muffin batter evenly into the prepared muffin tin. Sprinkle with a bit a brown sugar. Then bake for 20-24 minutes until the tops spring back when gently pushed, and toothpick comes out clean, or internal temperature is about 200F.
Cool for a minute in the muffin tin then remove to a wire cooling rack to cool until room temperature.
Make sure muffins are at room temperature before covering and freezing.