In a large bowl, combine the flour, sugar, baking powder, and salt. In a medium sized bowl whisk together the milk, butter, and eggs until combined. Pour the wet ingredients and lemon zest into the flour mixture and mix until just combined. Pour into prepared pan and bake for 45-50 minutes, until browned and a toothpick inserted in the center has only moist crumbs. Remove bread from oven and place on a wire rack.