Preheat oven to 180°C (350°F) and prepare a muffin mold with muffin liners.
Optional if you use apple cider vinegar. In a medium bowl or glass combine milk and apple cider vinegar. Stir with a spoon and set aside for later.
Grate the zucchini. Once grated, squeeze the vegetable thoroughly to remove any extra water using a clean towel. Set aside for later.
In a large mixing bowl beat the egg together with applesauce, maple syrup, vegetable oil, vanilla extract and a pinch of salt. Whisk until combined, then add the grated zucchini and stir well.
Sift oat flour, cocoa powder, baking powder and baking soda into the wet ingredients. Gradually pour in the milk mixture prepared before while mixing with a spatula or hand whisk. Stir until you get a lump-free smooth batter.
Fold through the chocolate chips.
Fill ⅔ of each muffin liner with the batter, sprinkle with more chocolate chips and bake in hot oven for 20 to 25 minutes. Make sure you do not overbake the muffins; they are ready when a toothpick inserted into the center comes out clean.
Notes
The apple cider vinegar is optional but it gives moister and fluffier muffins. Stirring milk and apple cider vinegar together produces a mixture that is similar to buttermilk, an ingredient which is often used for achieving fluffier dessert textures.