1Preheat oven to 350 degrees F. Coat a 9- by 5-inch loaf pan with cooking spray.
Whisk milk, eggs, sugar, oil, and vanilla in a medium bowl. Stir in zucchini. Combine flour, baking powder, cinnamon, and salt in a large bowl. Add the wet ingredients and chocolate chips to the dry ingredients; stir until just combined. Transfer the batter to the prepared pan.
Bake until golden brown and a wooden skewer inserted in the center comes out clean, 50 minutes to 1 hour. Cool in the pan for 10 minutes, then turn out onto a wire rack. Let cool for at least 1 hour before slicing.