Preheat oven to 400ºF. Spray a 12-cup muffin tin with cooking spray and set aside.
Layer grated zucchini in paper towels to get excess moisture off.
Cream butter and sugar in a mixing bowl. Add applesauce and egg and combine.
Sift together flour, baking powder, salt and cinnamon in a separate bowl. Pour vanilla extract into the cup of milk.
Add about 1/3 of flour mixture to mixing bowl and mix on low until just combined. Don't overmix. Add half of the milk and mix until just combined. Add another 1/3 of the flour mixture and mix until barely combined. Add the remaining milk and blend. Finish the rest of the flour mixture, making sure to not overmix.
Fold in zucchini and chocolate chips and divide batter into muffin cups. Bake in preheated oven for 15-20 minutes, or until tops are barely golden brown and spring back when touched. Let cool and remove from pan. Enjoy!