Preheat oven to 350 degrees.
Spray loaf baking pan (8 x 4 x 2-½") with cooking spray.
In a medium-sized mixing bowl, beat together the eggs, sugar, oil, and vanilla.
In large mixing bowl, combine the the flour, cinnamon, baking soda and baking powder.
Mix the dry ingredients with zucchini and nuts (optional) and then mix into the eggs-sugar mixture.
Blend well by hand.
Pour batter into the loaf pan leaving about ½ inch from the top.
Bake in preheated oven for 50 minutes; keeping in mind not to overcook, you want this cake MOIST.
For the frosting, beat all the ingredients together until light and fluffy.
Spread generously on top of cake/bread.
This zucchini cake/bread can easily be frozen when wrapped in heavy freezer aluminum foil.