Pre-heat the oven to 425°F. Grease 18 cups of two muffin pans with butter or line with paper liners.

Combine the flour, cocoa powder, baking powder, baking soda, and salt in a bowl.

In a second bowl and using an electric mixer, beat the oil and sugar together until light and fluffy. Add the milk, vanilla extract and eggs one at a time. Mix until well combined. Add the dry ingredients to the wet ingredients and stir only until just combined - do not over-mix. Stir in the grated zucchini and then 1½ cups of the chocolate chips.

Pour the batter evenly into the prepared muffin pans. Sprinkle the remaining chocolate chips on top of the batter in the muffin tins.

Bake at 425° for 8 minutes. Then turn down the oven temperature to 350°F. Do not open the oven door. Bake for another 10 t0 15 minutes until a toothpick inserted in the center of the muffin comes out clean from batter.

Transfer the muffin pan to a cooling rack and let it cool in the pan for 5 minutes. Then remove the muffins from the pan and cool completely on the wire rack. Serve warm or at room temperature or store muffins at room temperature for 3 to 5 days in an airtight container or zipper sealed bag. You can also freeze the muffins for up to 3 months.