Preheat your oven to 350°F and grease a 9x5 inch loaf pan or similar size, making sure to coat the bottom and sides evenly. While the oven heats, whisk together the cocoa powder, all-purpose flour, baking soda, baking powder, salt, cinnamon, and espresso powder in a large bowl. Whisking rather than just stirring helps aerate the dry ingredients and prevents lumps, which is especially important with cocoa powder. Set this mixture aside—I find that having your dry ingredients ready before mixing the wet ones keeps the batter from becoming overmixed, which can make the bread dense.

In a second large bowl, whisk together the vegetable oil, granulated sugar, and packed brown sugar until well combined. Add the room temperature eggs and vanilla extract, whisking until the mixture is smooth and slightly lighter in color. Fold in the mashed bananas until just incorporated, then add the finely shredded and squeezed-dry zucchini, folding gently to distribute evenly throughout. The zucchini should be as dry as possible—I squeeze it in a clean kitchen towel to remove excess moisture, which prevents a soggy bread and helps achieve better texture.

Pour the wet ingredient mixture into the bowl with the dry ingredients. Using a spatula or wooden spoon, gently fold the two mixtures together, stirring just until the dry ingredients are moistened and no flour streaks remain—this typically takes 10-15 gentle folds. Don't overmix, as this develops the gluten and can result in a tough, dense bread. Fold in the semi-sweet chocolate chips, distributing them evenly throughout the batter.

Pour the batter into your prepared loaf pan, smoothing the top gently with a spatula. Place the pan in the preheated 350°F oven and bake for 45-60 minutes. The bread is done when a toothpick inserted into the center comes out with just a few moist crumbs (not wet batter). Since every oven runs differently, start checking around the 45-minute mark. The top should be deeply browned and may have a slight crack down the center.

Remove the bread from the oven and let it cool in the pan for 10-15 minutes. This allows the crumb structure to set properly and makes it easier to remove from the pan. Turn the bread out onto a wire rack to cool completely before slicing. I like to wait until it's completely cool before slicing—this helps prevent the bread from crumbling, though warm slices with butter are absolutely delicious if you can't resist sampling it earlier!