Heat oven to 325°F (165°C). Grease a 9-by-5-inch loaf pan and line with parchment paper.

In a large bowl, whisk eggs, brown sugar, oil, vanilla, and salt until smooth and glossy.

Add grated zucchini and mix with a spatula until incorporated.

Sift flour, cocoa powder, baking powder, and baking soda into the bowl. Stir just until combined.

Add all but 1 tablespoon of chocolate chips to the batter and mix until evenly distributed.

Transfer batter to the prepared pan. Sprinkle with coarse sugar and reserved chocolate chips, pressing them in slightly.

Bake 75–80 minutes, until a skewer comes out with a few moist crumbs or melted chocolate.

Cool in the pan for 15 minutes. Lift out using parchment and cool completely on a rack before slicing.