Preheat oven to 325°. Grease a loaf pan.
Combine flour, cinnamon, baking soda, baking powder, and salt in a medium bowl. Set aside.
Grate zucchini and set aside. Do not wring out the zucchini liquid.
Mix sourdough starter and eggs.
Add grated zucchini, vanilla extract, and melted butter.
Pour dry ingredients into wet ingredients. Add chocolate chips.
Mix until just combined.
Pour batter into loaf plan.
Bake for one hour or until a toothpick in the center comes out clean.