Heat oven to 350°F and add prepare a muffin tin with parchment liners.
In a large mixing bowl, whisk together flour, baking powder, baking soda, cinnamon and salt until combined. Set aside.
In a separate mixing bowl, whisk together egg, maple syrup, milk, coconut oil, apple cider vinegar, and vanilla extract until combined. Pour this mixture into the dry ingredient mixture, and stir gently with a spoon until just combined - be careful not to overmix!
Stir in the zucchini. If you want to add the optional oats, add them in, too.
Finally add in the chocolate chips.
Divide batter into 12 muffin and cook for 18-20 minutes or until a toothpick comes out clean.
Transfer pan to a cooling rack and enjoy slightly cooled. Store in a sealed container for a few days, or freeze.