Preheat oven to 350F. Spray a muffin tin with cooking spray and set aside.
Combine flax and water in a small bowl and set aside to gel.
Using paper towels, squeeze liquid out of zucchini. Add zucchini to a large bowl. Add bananas and mash with a fork. Add coconut oil and vanilla to bowl and stir until well combined. Stir in flax mixture.