Preheat your oven to 350°F (177°C). Grease a 9×5-inch loaf pan or an 8×4-inch loaf pan (for a taller loaf) with nonstick spray and set aside. In a large bowl, whisk together the flour, cocoa powder, baking soda, baking powder, salt, and espresso powder until well combined. Stir in the chocolate chips and set the mixture aside. In a medium bowl, whisk the eggs, oil, yogurt, granulated sugar, and vanilla extract until smooth. Gradually add the wet ingredients to the dry ingredients, gently whisking to combine. Fold in the shredded zucchini; the batter will be thick. Pour the batter into the prepared pan and bake for 45–55 minutes, loosely covering the bread with aluminum foil halfway through baking to prevent the top from over-browning. The 9×5-inch pan usually needs about 45 minutes, while the 8×4-inch pan takes closer to 55 minutes. Since ovens vary, start checking doneness at around 45 minutes by inserting a toothpick into the center—it should come out clean with just a few moist crumbs. Remove the bread from the oven and let it cool in the pan on a wire rack for 1 hour. While still warm, you can gently press a few extra chocolate chips onto the top for decoration if desired. Then, remove the bread from the pan and place it directly on the wire rack to cool completely. Store the bread covered at room temperature for up to 5 days or refrigerate for up to 1 week.