Preheat oven to 425°F. Line 2 jumbo muffin tins with 9 paper liners.
In a large bowl, sift together flour, cocoa powder, baking powder, baking soda, salt and espresso powder.
330 g all-purpose flour, 63 g cocoa powder, 1 tablespoon baking powder, 1/2 teaspoon baking soda, 1 teaspoon espresso powder, 1/2 teaspoon salt
In a separate bowl, whisk together oil, sugars, eggs, milk and vanilla.
1/2 cup canola or vegetable oil, 132 g granulated sugar, 71 g brown sugar, 2 large eggs, 1 cup milk, 1 teaspoon vanilla extract
Pour wet ingredients into dry. Gently stir together with rubber spatula.
Add shredded zucchini and chocolate chunks and stir until just combined.
250 g 2 cups shredded zucchini, excess moisture squeezed out, 175 g 1 cup chocolate chunks or chips
Divide batter into 9 paper liners, filling each about 7/8 full.
Bake at 425°F for 5 minutes. Turn oven temperature down to 350°F and continue baking for 18-22 minutes when a toothpick comes out clean when inserted into the center.
Remove from the tin once cool enough to handle and transfer to a cooling rack.