Preheat oven to 350℉. Grease a 9x5-inch loaf pan and line with parchment paper. Set aside.

In a medium bowl, whisk together flour, cinnamon, baking soda, and salt. Set aside.

In a large bowl, whisk together the granulated and brown sugars, vegetable oil, egg, and vanilla extract. Add sourdough discard and mix until smooth.

Add the dry ingredients to the wet ingredients and stir until combined and no dry spots remain.

Shred the zucchini on a paper towel. Cover with another paper towel and press to remove any excess moisture. Fold the shredded zucchini into the batter. If adding chocolate chips (optional), fold in ½ cup of chocolate chips during this step as well, reserving 2 Tablespoons of chocolate chips for the topping.

Pour the batter into the prepared baking pan, then sprinkle with turbinado sugar. If adding chocolate chips (optional), sprinkle the 2 Tablespoons of reserved chocolate chips on top.

Bake for 55-60 minutes or until a toothpick inserted in the center of the loaf comes out clean, or the internal temperature of the loaf reaches 205℉.

Remove from the oven and let the loaf cool in the pan for 10 minutes, then transfer to a cooling rack to cool fully.