Step 1

Heat oven to 350°F. Coat 12-cup muffin pan with nonstick spray or line with cupcake liners.

Step 2

In large bowl, whisk together flour, wheat bran, cocoa powder, baking soda and salt. In medium bowl, whisk eggs, buttermilk, sugar, oil and vanilla.

Step 3

Make well in center of dry ingredients and gradually whisk in buttermilk mixture until just incorporated.

Step 4

Fold zucchini and 1/4 cup chocolate chips into batter; divide among prepared muffin cups (about 1/3 cup each). Top with remaining 1/4 cup chocolate chips and bake until toothpick inserted in center comes out mostly clean, 25 to 30 minutes. Let cool in pan 10 minutes. Using small offset spatula, carefully remove muffins to wire rack to cool completely.