Preheat your oven to 350°F (175°C) and prepare two 8x4-inch loaf pans, greasing them with butter or non-stick spray.

In a medium bowl, whisk together the all-purpose flour, salt, baking powder, baking soda, and ground cinnamon until combined.

In a large mixing bowl, blend the melted butter, light brown sugar, granulated sugar, vanilla extract, and beaten eggs until creamy.

Gently fold the dry mixture into the wet ingredients until just combined, ensuring not to overmix.

Fold in the shredded zucchini and any optional mix-ins, distributing them evenly.

Divide the batter between the prepared pans and smooth the tops. Bake for 55-60 minutes or until a toothpick comes out clean.

Let the pans cool for about 15 minutes, then remove the loaves and let them cool completely on a wire rack.