Preheat the oven to 350°F (175°C). Grease a 9×5-inch loaf pan or line it with parchment.

Toss the shredded zucchini in a clean kitchen towel or paper towel and press to remove extra liquid. You want it damp, not soggy.

Whisk together the flour, baking powder, baking soda, and salt in a large mixing bowl so the leaveners are evenly dispersed.

Make a quick buttermilk: combine the milk and vinegar in a small bowl and let it rest for a minute. Whisk in the egg and the melted butter until smooth.

Pour the wet mixture into the dry ingredients and fold gently with a spatula until just combined — a few streaks of flour are okay. Overworking will tighten the crumb.

Fold in the drained zucchini, grated cheddar, and sliced green onions until they’re distributed through the batter. Add a grind of black pepper if you like a savory lift.

Spoon the batter into the prepared pan and smooth the top. Bake for about 55–65 minutes, or until a toothpick comes out clean from the center. Oven times vary, so start checking at 50 minutes.

Let the loaf rest in the pan for 10 minutes, then transfer it to a wire rack to cool before slicing.