Prep the pan: Preheat the oven to 350°F. Grease a 9x5-inch loaf pan and line with parchment paper for easy removal.
Shred the zucchini: Wash and shred zucchini with a box grater. Measure 1½ cups. Lightly blot if very watery, but don’t squeeze dry.
Mix dry ingredients: In a large bowl, whisk flour, cocoa powder, baking soda, baking powder, salt, and optional espresso powder.
Mix wet ingredients: In another bowl, whisk eggs, oil, Greek yogurt or sour cream, sugar, and vanilla until smooth.
Combine the batter: Add wet ingredients to dry ingredients and stir gently. Fold in shredded zucchini and chocolate chips until just combined.
Fill the pan: Spread batter into the prepared loaf pan. Smooth the top and sprinkle with extra chocolate chips.
Bake: Bake for 45–55 minutes, or until a toothpick comes out with moist crumbs but no raw batter. Tent with foil if the top browns too quickly.
Cool and slice: Cool in the pan for 15 minutes, then transfer to a wire rack. Let cool completely for cleaner slices.
