Butter two 5 x 9-inch loaf pans then coat with sugar. Set aside.
Preheat oven to 350ยบ.
Whisk together the flours, cinnamon, baking powder, baking soda, and salt. Set aside.
In a large bowl, whisk the eggs, then add the sugars, whisking till mixture becomes a pale yellow color, about 2-3 minutes.
Add the oil and vanilla and whisk to combine.
Mix in zucchini, then add the dry ingredients with a rubber spatula. Mix till just combined.
Divide batter between the two pans and bake for 60-70 minutes or till a toothpick inserted into the center comes out clean.
Let cool for about 10-15 minutes before removing the loaves to a wire rack to finish cooling.
Bread tastes best when served at room temperature and is even better the next day.
