Preheat the oven to 350 degrees F. Grease a 9 x 5-inch loaf pan and line it with parchment paper.
Whisk together the flour, cocoa powder, baking soda, baking powder, salt, and cinnamon in a medium bowl.
In a large bowl, whisk together the extra virgin olive oil, brown sugar, granulated sugar, eggs, and vanilla extract until smooth.
Stir in the shredded zucchini and sour cream until fully combined.
Add the dry ingredients to the wet ingredients and stir until no dry streaks remain. Fold in the chocolate chips and nuts, if using.
Transfer the batter to the prepared loaf pan and smooth the top.
Bake for 55-65 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs attached.
Cool the bread in the pan for 15 minutes, then transfer to a wire rack to cool completely before slicing.