Preheat oven to 350°F. Grease a 9x5x3” loaf pan with nonstick cooking spray.
Whisk flour, cinnamon, salt, and baking soda in a small bowl. Set aside.
Stir oil and ¾ cup (150g) sugar with a wooden spoon or spatula. Stir in banana, eggs, milk, vinegar, and vanilla.
Mix in dry ingredients until just incorporated, then stir in zucchini. Pour into prepared pan.
Combine ¼ cup sugar and 1 teaspoon cinnamon in a small bowl. Sprinkle some evenly over the top of the batter. You will have leftover cinnamon sugar.
Bake for 40-50 minutes until a toothpick comes out in the very center with just a few crumbs. The edges will be a dark brown and there will be a nice crack down the center.
Cool completely before removing loaf from pan, but you can cut slices from the pan after it’s cooled for about 15-20 minutes.
