Preheat the oven to 350 degrees and spray a 12 cup muffin pan with cooking spray or use cupcake liners. Place the butter in a microwave safe bowl and heat until the butter is melted.
In a large bowl add the eggs and beat with a fork, then stir in the zucchini, melted butter, sugar, and vanilla and mix well. Then add the salt, flours, baking soda, and spices and stir until combined.
Fill the muffin tins about 2/3 full. Bake for about 23-26 minutes or until a toothpick inserted in the middle comes out clean.
Allow to cool for about 10 minutes. While the muffins are cooling, mix the powdered sugar and lemon juice together in a bowl, and then spoon over the muffins.