Preheat the oven to 350F degrees. Line the bottom of an 8 ½ by 4 ½ inch loaf pan with parchment paper, then grease and flour the sides.
Gently blot the grated zucchini with a paper towel to remove excess water.
In a medium bowl whisk together the flour, cocoa, baking soda and salt.
In a large bowl whisk together the melted butter, sugar, eggs and vanilla extract until there are no chunks of sugar.
Gently fold the flour mixture into the oil mixture.
Once almost combined, stir in the grated zucchini.
Fold in the chocolate chips.
Pour the batter into the prepared pan, and bake for 45-55 minutes until the top is firm to the touch and an inserted toothpick comes out clean (except for melted chocolate chips).
Cool fully before cutting into slices.