Preheat the oven to 350 F.

Grease a 9×5 bread loaf tin with butter. This will help it pop out of the pan when you are done baking.

Grate the zucchini and set aside.

In a large mixing bowl, combine the brown and granulated sugars, applesauce, and sourdough starter. Whisk until combined well.

Add in the eggs, and vanilla and whisk until combined

In a medium mixing bowl, whisk together the flour, cinnamon, nutmeg, baking powder, baking soda, and salt.

Add the dry ingredients to the wet ingredients and fold until just barely combined together.

Fold in the shredded zucchini and chopped walnuts.

Evenly spread the batter into the prepared bread pan.

Bake for 60-65 minutes, or until a toothpick inserted in the center comes out clean.

Allow to cool for 10-15 minutes in the pan, and then turn out of the pan (carefully) onto a wire rack to finish cooling.