Preheat your oven to 350°F (175°C). Line your muffin tin with paper cups or lightly coat it with oil to prevent sticking.
Mix 1 tablespoon ground flaxseed in a small bowl with 3 tablespoons water. Let it rest for 5 minutes until it thickens up.
Grate 1 cup of zucchini and squeeze the excess moisture using a paper towel or kitchen cloth.
Combine rolled oats, whole wheat flour, baking powder, baking soda, cinnamon, and salt in a large bowl.
Whisk together the flax egg, melted coconut oil, maple syrup, almond milk, and vanilla extract in a separate bowl.
Pour the wet ingredients into the dry ingredients and stir until just combined. Gently stir in the grated zucchini and any extras you’d like to add.
Fill each muffin cup with batter, aiming to fill them about three-quarters of the way.
Bake for 18-20 minutes or until a toothpick inserted in the center comes clean.
Let the muffins rest in the pan for 5 minutes, then transfer them to a wire rack to cool off completely. Enjoy warm or at room temperature.