Prep: Line the bottom of a 5×9 inch loaf pan with parchment and grease the sides. Preheat the oven to 360°F.
Make batter: Add zucchini, oil, honey, Greek yogurt, eggs and vanilla to a large mixing bowl and stir until well combined. Combine flour, cocoa powder, baking powder, baking soda and salt in a separate bowl and stir until combined. Add dry to wet ingredients and fold just until combined – do not overmix, a few lumps are fine! Fold in the chocolate chunks.
Bake: Transfer the batter to the prepared loaf pan and bake the bread in the preheated oven for 45-50 minutes, or until a toothpick inserted comes out clean.