Preheat oven to 375 degrees F.
Line a muffin pan with paper liners or spray with cooking spray.
In a large bowl, whisk together flour, brown sugar, baking soda, baking powder, salt, cinnamon, and all-spice.
In another bowl, whisk together buttermilk, applesauce, oil, egg, and vanilla extract.
Pour the wet ingredients over the dry ingredients and mix with a wooden spoon or spatula until just combined.
Gently stir in the grated apple, zucchini,chopped apples and walnuts.
For Topping, combine sugar and cinnamon in a small bowl stirring well.
Fill the prepared muffin pan with batter, filling each cup about 3/4 the way full.
Sprinkle each muffin with cinnamon sugar topping.
Bake for 20 minutes, or until muffins are golden and a toothpick inserted in the center of a muffin comes out clean.
Let muffins cool before serving.