Preheat the oven to 350°F.
Grease two loaf pans and set aside.
In a large mixing bowl, whisk together the flour, salt, baking powder, baking soda, and cinnamon.
In a separate mixing bowl, whisk together the brown sugar, granulated sugar, and melted butter until well combined.
Add the eggs and vanilla extract, mixing until smooth.
Gradually add the dry ingredients to the wet ingredients, stirring just until a batter forms.
Gently fold in the shredded zucchini and walnuts, if using.
Divide the batter evenly between the prepared loaf pans, filling each about two-thirds full to allow room for the bread to rise.
Bake for 55-60 minutes, or until a toothpick inserted into the center comes out clean.
Let the loaves cool in the pans for 15 minutes before transferring them to a wire rack to cool completely.
Slice and serve when ready.