Preheat your oven to 350°F (175°C) and spray a 9x5 inch bread pan with non-stick cooking spray.

Squeeze out excess moisture from the grated zucchini using a clean paper towel.

In a large mixing bowl, combine flour, baking powder, baking soda, and salt. Whisk thoroughly.

In a separate bowl, mix milk and vinegar to create buttermilk, then add melted butter and egg. Whisk until smooth.

Pour the wet mixture into the dry ingredients and stir until just combined, leaving a few streaks of flour.

Fold in shredded zucchini, cheddar cheese, and green onions until evenly distributed.

Pour the batter into the prepared pan and smooth the top.

Bake for about 60 minutes until golden brown and a toothpick comes out clean.

Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely for at least 30 minutes.