Preheat oven to 350°F. Line a 12-cup muffin tin with liners and spray lightly with nonstick spray.
In a medium bowl, whisk together flour, flaxseed, baking soda, baking powder and salt.
In a large bowl, combine mashed banana, melted butter, honey, vanilla, egg and buttermilk. Whisk until smooth. Add dry ingredients and mix until just combined. Gently stir in zucchini.
Divide batter evenly among muffin liners (about 3 tablespoons each). Bake for 20-22 minutes, or until a toothpick inserted into the center comes out mostly clean. Let cool 10 minutes in the pan, then transfer to a wire rack to cool completely.
Spread tops with Chocolate Snack Spread and enjoy.