Preheat oven to 350 F. Grease 1 regular/large loaf pan, or line with parchment paper.
In a large bowl, whisk together flours, baking powder, spices, xanthan gum, baking soda, and salt. Set aside.
In a separate bowl - a small or medium bowl - whisk together sugar, vegetable oil, yogurt, eggs, and vanilla until smooth and well combined. Stir in the zucchini.
Add the wet ingredients mixture to the mixing bowl of dry ingredients, along with the nuts. Use a wooden spoon or rubber spatula to stir just until combined.
Pour batter into prepared loaf pan.
Bake for about 1 hour, or until crust is a rich golden brown, and knife inserted into middle of loaf comes out clean.
Once fully cooked, remove from oven and allow to cool for at least 15-20 minutes before cutting - if you’ve got that kind of patience! You can use a wire rack to help it cool faster, if you like.
Leftovers can be cooled to room temperature, wrapped in Saran wrap and stored in the fridge for 5 days or so.
Notes
Best served at room temperature or - ideally - warmer.