Preheat oven to 350º F (175 degrees C). Lightly grease a 9x5 inch loaf pan.
In a large bowl, combine cocoa powder, eggs, sugar, oil, grated zucchini and vanilla; beat well. Stir together the flour, baking soda, salt, cinnamon and chocolate chips. Add to wet ingredients just to moisten. Pour batter into prepared loaf pan.
Bake in preheated oven for 60 to 70 minutes, or until a toothpick inserted into the center of a loaf comes out clean.