Preheat the oven to 350°F (175°C).

Grease a 9×5-inch loaf pan and line it with parchment if you like.

In a large bowl, whisk together the gluten-free flour, cocoa powder, baking soda, baking powder, and salt.

Grate the zucchini and gently squeeze out excess water.

In a separate bowl, whisk the maple syrup (or honey), oil, eggs, and vanilla extract until smooth.

Stir the grated zucchini into the wet ingredients.

Add the dry ingredients to the wet mixture and fold with a spatula until just combined.

If using, fold in the dark chocolate chips.

Pour the batter into the prepared loaf pan and smooth the top.

Bake for 50–60 minutes, or until a toothpick inserted in the center comes out with only moist crumbs.

Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.