1. 1. Prepare Your Baking Pan and Oven: Preheat your oven to 350 F (175 C). Lightly grease and flour a 9×5-inch loaf pan, or line it with parchment paper, leaving an overhang on the long sides to easily lift the bread out later.

2. 2. Combine Dry Ingredients: In a large bowl, whisk together the all-purpose flour, whole wheat flour, baking soda, baking powder, cinnamon, nutmeg, and salt. Make sure there are no lumps and all ingredients are evenly distributed.

3. 3. Mix Wet Ingredients: In a separate medium bowl, whisk together the sourdough discard, unsweetened applesauce, granulated sugar, brown sugar, vegetable oil, eggs, and vanilla extract until smooth and well combined.

4. 4. Combine Wet and Dry Mixtures: Pour the wet ingredient mixture into the dry ingredient mixture. Stir gently with a spatula until just combined. Be careful not to overmix; a few streaks of flour are perfectly fine. Overmixing can lead to a tough bread.

5. 5. Fold in Zucchini: Gently fold in the grated zucchini. Ensure it’s evenly distributed throughout the batter. Remember to squeeze out any excess moisture from the zucchini before adding it to prevent a soggy loaf.

6. 6. Pour into Loaf Pan and Bake: Pour the batter into the prepared loaf pan and spread it evenly. Bake for 50-60 minutes, or until a wooden skewer or toothpick inserted into the center comes out clean. The top should be golden brown and spring back lightly when touched.

7. 7. Cool Before Slicing: Once baked, remove the loaf pan from the oven and let the bread cool in the pan for about 10-15 minutes. This allows it to set properly. Then, carefully lift the bread out of the pan using the parchment paper overhang (if used) or invert it onto a wire rack to cool completely before slicing and serving.