Preheat the oven to 350°F. Spray a 9×5-inch loaf pan with cooking spray.
In a medium bowl, whisk together the gluten-free flour, cocoa powder, baking soda, baking powder, salt, and chocolate chips.
In a large bowl, whisk together the sugar, sour cream, oil, eggs and vanilla. Stir in the grated zucchini.
Add the dry ingredients to the wet ingredients and mix with a rubber spatula, until fully combined.
Pour the batter into the prepared loaf pan. Bake for 50-60 minutes, until a toothpick inserted into the center of the loaf comes out clean.
Remove from the oven and cool in the pan for 5 minutes. Remove the loaf from the pan and transfer to a wire rack to cool completely.