Position oven rack to the centre and preheat oven to 350ºF (177ºC)
Use the largest holes in a box grater to grate the zucchini into big shreds. Squeeze out any excess moisture from the zucchini and transfer the zucchini to a large bowl.
Add 2 eggs, melted butter, brown sugar, yogurt and vanilla and whisk together.
Then add flours, baking powder, baking soda, cinnamon, nutmeg and salt and mix until just combined. Fold in any optional add-ins. Batter will be slightly thick.
Prepare parchment-lined 9x5-inch loaf pan and pour batter into pan.
Bake for 55-60 minutes until deeply golden and a tester inserted comes out clean. Let bread cool in pan for 30-45 minutes, then remove from pan, slice and serve!