Preheat oven to 350°F. Line a 12-cavity muffin pan with liners and lightly coat with cooking spray. Set aside. Make sure all wet ingredients are at room temperature to keep the batter from clumping.
Grate zucchini on the small side of a box grater. Use cheesecloth or a few paper towels to squeeze it a few times and remove some of the liquid. Then lightly add it into a 1-cup measuring cup for the perfect amount.
In a small bowl, mash the banana well. The banana helps bind these muffins, and the riper the banana, the better! I like using electric hand mixers and blending until the consistency is similar to thick applesauce. Measure after mashing.
In a large bowl, whisk together the room temp Greek yogurt, vanilla extract, egg, coconut oil, honey, mashed banana, and brown sugar until smooth.
Add oats to a high-powered blender and blend into a flour-like consistency. Add the blended oats, baking soda, salt, cinnamon, and flour to the wet ingredients. Mix until a few streaks of flour remain, then add the zucchini. Stir just until combined; avoid over-mixing.
Divide batter evenly among all 12 muffin cavities. Bake for 18 to 22 minutes or until a toothpick inserted into the center comes out clean and the tops are lightly golden. Avoid overbaking, which can dry out the muffins. Let cool for 5 to 10 minutes, then use a fork to gently remove muffins to a wire cooling rack.
Notes
Storage: Store in an airtight container in the fridge; let stand at room temperature for 30 minutes to 1 hour before eating. Best enjoyed within 1–3 days.