Preheat your oven to 350°F (175°C). Grease a 9x5-inch loaf pan or line it with parchment paper for easy removal.
In a large mixing bowl, whisk together the flour, cocoa powder, baking soda, baking powder, salt, and cinnamon until well combined.
In another bowl, mix the granulated sugar, brown sugar, vegetable oil, eggs, and vanilla extract until smooth.
Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Do not overmix.
Fold in the grated zucchini and chocolate chips until evenly distributed.
Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean. If the top starts to brown too quickly, cover it loosely with aluminum foil.
Allow the bread to cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely.