Preheat the oven to 350°.
In a small bowl, mix the ground flax and water. Set aside for five minutes to make a flax egg.
Combine the apple cider vinegar with almond milk and set aside, also for 5 minutes.
Shred the zucchini using a box grater. Measure out 1 cup, packed.
In a medium bowl, mash the banana with no lumps; it should be liquified.
In a large bowl, combine the flour, baking powder, baking soda, cinnamon, and salt.
To the bowl with the banana add the flax egg, curdled milk, and maple syrup.
To the large bowl with the flour, add the wet ingredients. Stir slowly to mix wet and dry, but do not over-mix. Once the ingredients are combined, fold in the shredded zucchini. Add the chopped walnuts and chocolate chips if you choose.
Prepare a muffin tin. I use silicone cups. Or you could use paper liners. Fill the cups 3/4 full; you should have enough batter for 12 muffins.
Bake 30-35 minutes on the center rack, until tops are golden brown. Allow to cool completely before serving.