Preheat your oven to 350˚F and prepare two 8x4 inch loaf pans by spraying with cooking spray. Combine the all-purpose flour, brown sugar, granulated sugar, baking soda, cinnamon, and salt in a medium bowl. Give it a gentle whisk to mix everything, then set the bowl aside.
Now, take a large bowl and beat the eggs in it. Add the grated zucchini, vegetable oil, sour cream, and vanilla to the eggs. Mix all these wet ingredients until well combined.
Add the dry ingredients to the wet mixture. Stir them in gently until just combined. Don't overmix; we want the bread to be nice and light!
Next, fold the chopped walnuts into the batter if desired. They will add a delightful crunch and nutty flavor to the bread.
Now, divide the batter evenly between the two prepared loaf pans.
Bake the zucchini bread in the preheated oven for 50-60 minutes or until a toothpick inserted into the center of the bread comes out clean. This is our surefire way to know it's perfectly baked!
Once done, take the pans out of the oven and allow them to cool for about 5 minutes. Then, gently remove the bread from the pans and place them on a wire rack to cool completely.