Preheat the oven to 350°F (175°C) and prepare a 9x5-inch loaf pan by greasing it or lining it with parchment paper.
In a mixing bowl, combine the grated zucchini with a pinch of salt and let it sit for about 10 minutes. Squeeze out excess moisture using a clean kitchen towel.
In a separate large bowl, whisk together the all-purpose flour, cocoa powder, baking soda, baking powder, salt, and ground cinnamon until combined.
In another bowl, beat together the granulated sugar, packed brown sugar, eggs, vegetable oil, and vanilla extract until smooth and creamy.
Gradually add the dry mixture to the wet ingredients, stirring gently until just combined.
Fold in the grated zucchini, semi-sweet chocolate chips, and walnuts or pecans until evenly distributed.
Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake for 50 to 60 minutes, checking for doneness with a toothpick.
Once baked, let the bread cool in the pan for 10 minutes before transferring to a wire rack to cool completely.
Notes
Serve warm, possibly with a dusting of powdered sugar or a dollop of whipped cream.