Preheat oven to 350°F (177°C). Grease a 9×5-inch loaf pan or 8.5×4.5-inch loaf pan (for a taller loaf) with nonstick spray. Set aside.

In a large bowl, whisk the flour, cocoa powder, baking soda, baking powder, salt, and espresso powder together until combined. Mix in the chocolate chips. Set aside.

In a medium bowl, whisk the eggs, oil, yogurt, granulated sugar, and vanilla together until combined. Slowly pour the wet ingredients into the dry ingredients and gently whisk to combine. Fold in the zucchini. The batter is very thick.

Bake for 45–55 minutes, making sure to loosely cover the bread with aluminum foil halfway through to prevent the top from over-cooking. The bread is done when a toothpick inserted in the center comes out clean with only a few small moist crumbs. The 9×5-inch pan takes closer to 45 minutes, and the 8×4-inch pan takes closer to 55 minutes. All ovens vary, so begin checking around the 45-minute mark.

Remove bread from the oven and allow the bread to cool in the pan set on a wire rack for 1 hour. While it’s still warm, I gently press a few more chocolate chips into the top; this is optional and only for looks.

Remove bread from the pan and place the loaf directly on the wire rack to cool completely.

Cover and store bread at room temperature for 5 days or in the refrigerator for up to 1 week.