Preheat your oven to 325°F.

Grease and line a standard 9-inch x 5-inch loaf pan and set it aside. In a small microwave-safe bowl, place the chopped chocolate and microwave in 30-second bursts at 60% power, stirring in between, until smooth.

Set the chocolate aside to cool briefly.

In a large bowl, place flour, xanthan gum, cocoa powder, salt, baking soda, baking powder, and granulated sugar, and whisk to combine.

Place the chocolate chips in a separate small bowl, add 1 teaspoon of the dry ingredients to the chips and toss to combine. Set the chips aside.

Add 1 1/2 cups (150 g) of the grated zucchini to the dry ingredients and stir to combine, breaking up any clumps of grated zucchini.

In a blender or food processor, place the remaining 1/2 cup (50 g) grated zucchini, eggs, oil and vanilla, and blend or process until smooth.

Add the melted chocolate, and blend once more to combine.

Create a well in the center of the bowl of dry ingredients, pour in the wet ingredients and mix to combine. The batter will be soft.

Add all but a few of the chocolate chips and reserved dry ingredients to the batter, and stir until the chips are evenly distributed throughout.

Scrape the batter into the prepared loaf pan, and smooth the top with a wet spatula.

Sprinkle the remaining chocolate chips evenly on top and press gently to help them adhere.

Place the loaf pan in the center of the preheated oven, and bake, rotating once, until a toothpick inserted in the center of each loaf comes out clean (about 50 minutes).

Remove the pan from the oven and allow to cool for at least 20 minutes in the loaf pan before transferring a wire rack to cool completely.

Slice and serve.