2 cups all-purpose flour
1/2 cup unsweetened cocoa, preferably Dutch-process
1/2 teaspoon baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
3 large eggs, lightly beaten
1 cup packed brown sugar
¾ cup canola oil
1 teaspoon vanilla extract
2 cups grated zucchini or yellow squash
1/2 cup chocolate chips
Preheat oven to 325°F. Coat two 8 1/2-by-4 1/2-inch loaf pans with cooking spray.
Whisk flour, cocoa, baking powder, baking soda, and salt in a large bowl.
Whisk eggs, sugar, oil, and vanilla in another large bowl until blended. Add to the dry ingredients and stir with a rubber spatula until just combined. Fold in squash and chocolate chips. Spoon the batter into the prepared pans, smoothing the tops.
Bake the loaves for 45 -50 minutes, or until a skewer inserted in the center comes out clean. Let cool in pans on a wire rack for 10 minutes. Invert onto the rack and cool completely.