Preheat your oven to 350°F (175°C) and grease a 9x5 inch loaf pan or line it with parchment paper for easy removal.
In a medium bowl, combine the grated zucchini with a pinch of salt and let it sit for 10 minutes. Then squeeze out excess moisture and set aside.
In another bowl, whisk together the all-purpose flour, cocoa powder, baking soda, baking powder, salt, and cinnamon. Set this dry mixture aside.
In a large mixing bowl, combine granulated sugar, brown sugar, vegetable oil, eggs, and vanilla extract. Mix until smooth and well combined.
Slowly incorporate the dry ingredients into the wet mixture, stirring gently until just combined. Avoid overmixing.
Gently fold in the grated zucchini along with the semi-sweet chocolate chips, white chocolate chips, and dark chocolate chunks until evenly distributed.
Pour the batter into the prepared loaf pan, smoothing the top with a spatula.
Bake in the preheated oven for 45-55 minutes, or until a toothpick inserted in the center comes out clean.
Once baked, remove from the oven and allow it to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.
Notes
Dust the top with powdered sugar and serve warm with whipped cream or vanilla ice cream.