Preheat oven to 350°F. Lightly spray a 9- by 5-inch loaf pan with nonstick cooking spray. Set pan aside.

Place the zucchini on a large, dry kitchen towel. Cover the zucchini fully with the towel and twist both ends to the towel to wring moisture from the zucchini. Transfer zucchini to a large cutting board. Chop the zucchini roughly. (You can skip the chopping the zucchini if you’d like. It just helps the bread to have a more uniform texture with no long string of zucchini scattered throughout the baked loaf.) Set the aside zucchini aside.

Whisk together millet flour, granulated sugar, sorghum flour, flaxmeal, ground cinnamon, ground allspice, baking powder, baking soda, salt, and xanthan gum. Add the water, eggs, and vegetable oil. Whisk until a thick batter forms. Switch to a flexible spatula and stir in the zucchini.

Spread batter evenly into prepared pan. Bake until golden brown, about 40 minutes. A cake tester interested into the center of the loaf should come out clean. Allow bread to cool in the pan for 10 minutes before turning out to a wire rack to cool completely.