Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners or lightly grease it.
Grate the zucchini and set aside.
In small glass or bowl, mix ground flax seed with 2 1/2 tablespoons of water to make flax-egg. Set aside.
In a large mixing bowl, combine wet ingredients: flax egg, vegetable oil, plant-based milk, apple cider vinegar, and vanilla extract. Then add in zucchini. Stir until well blended.
In a separate bowl, whisk together all the dry ingredients: flour, sugar, baking powder, baking soda, cinnamon, nutmeg, and salt.
Slowly add the dry ingredients to the wet mixture and stir until just combined. If desired, gently fold in added chopped nuts.
Fill the muffin cups about 3/4 full with the batter.
Bake for 20-22 minutes, or until a toothpick inserted into the center comes out clean.
Let the muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely. Enjoy warm or store for later!