Preheat your oven to 350 degrees. Spray 3 mini loaf pans with gluten-free cooking spray (or one standard 9-inch loaf pan) and set aside.
Place the shredded zucchini into some paper towels and gently squeeze out any moisture. Fluff the zucchini with a fork and set aside.
Put the all-purpose gluten-free flour, almond flour, baking powder, baking soda, xanthan gum, salt and cinnamon in a medium bowl and whisk to blend. In another large bowl add the brown sugar, canola oil, eggs, coconut milk, lemon juice and walnuts. Whisk thoroughly until smooth.
Add the dry ingredients to the wet and beat until combined. Fold in the grated zucchini (I always reserve just a little to sprinkle over the tops of the loaves) and the nuts.
Divide evenly between the pans, sprinkle over the reserved zucchini and bake for 35-40 minutes, or until a toothpick inserted in the center of a loaf comes out clean.
Cool for 5 minutes in the pan, then carefully turn out to cool completely on a rack.