In a large bowl, stir together flour, baking powder, baking soda, and salt.
In another bowl, mix together zucchini, brown sugar, and cinnamon. Stir in vanilla, egg, and milk.
Stir wet ingredients into flour mixture until just combined, then stir in walnuts.
Heat your griddle and spray with nonstick spray, if desired.
Stir melted butter into pancake batter.
Using a 1/4 cup scoop, scoop batter onto griddle. Cook pancakes until bubbles form and pop on the surface, then flip and cook for an additional 1-2 minutes. Repeat until all batter is used.
Serve with maple syrup and additional walnuts, if desired.