Step 1

Place a rack in the center of your oven and preheat to 350°F. Coat an 8.5 x 4.5-inch loaf pan with nonstick spray and line with parchment paper so that two opposite sides of the parchment over hang the pan a bit, like handles.

Step 2

Place the grated zucchini in a clean dish towel and squeeze well to wring out excess water.

Step 3

In a large mixing bowl, combine the all-purpose flour, whole wheat flour, cocoa powder, baking soda, and salt.

Step 4

In a separate bowl, whisk together the eggs, yogurt, sugar, honey, and vanilla until smooth.

Step 5

Add the wet ingredients to the dry ingredients and stir until mostly combined—the batter will be thick and seem dry at this point. Do not over-mix; some dry spots are fine.

Step 6

Add the zucchini; if desired, reserve a handful of chocolate chips for sprinkling on top, then add the rest to the batter. Using a rubber spatula, stir slowly and deliberately to combine the zucchini evenly with the batter. You’ll want to smush it around a bit so that the zucchini moistens the batter and everything is evenly combined. As soon as it looks evenly distributed, stop mixing.

Step 7

Scoop the batter into the prepared pan and smooth it into an even layer (your pan will be full to the brim). Sprinkle the reserved chocolate chips over the top. Bang the pan on the counter a few times to remove air bubbles.

Step 8

Bake the chocolate zucchini for 45 minutes, then rotate the pan 180°F, tent with foil and continue baking for another 25 to 30 minutes, or until a skewer or long, thin knife inserted in the center of the loaf comes out clean with just a few moist crumbs clinging to it (don't use a toothpick—it won't reach in far enough). You also can use an instant read thermometer to check for doneness—the bread should register 200°F.

Step 9

Place the pan on a wire rack and let the bread cool in the pan for 15 minutes. Using the parchment handles, lift the bread out of the pan and onto the wire rack. Let cool before slicing.