Preheat your oven to 350°F (175°C). This is essential for ensuring your muffins rise beautifully.
Line your muffin tin with parchment paper or muffin liners. This will help with easy removal after baking.
In a large mixing bowl, whisk together the granulated sugar, light brown sugar, and vegetable oil until combined. Add the eggs, one at a time, mixing well after each addition. Finally, stir in the vanilla extract.
In another bowl, sift together the all-purpose flour, cocoa powder, salt, baking soda, and ground cinnamon. This step ensures that your dry ingredients are well mixed and free of lumps.
Gradually add the dry ingredient mixture to the wet ingredients, stirring gently to combine. Be careful not to overmix; it’s okay if a few lumps remain.
Gently fold in the finely grated zucchini along with the semisweet chocolate chips and mini milk chocolate chips if using. The batter will be thick and chocolatey!
Scoop the batter into the prepared muffin tin, filling each cup about 2/3 full. This allows room for the muffins to rise.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean. The muffins should be puffed and slightly firm to the touch.
Once baked, remove the muffins from the oven and let them cool in the pan for about 5 minutes before transferring them to a wire rack to cool completely. Enjoy them warm or at room temperature!
