Moist Carrot Zucchini Cake with Cream Cheese Frosting

Moist Carrot Zucchini Cake with Cream Cheese Frosting
Ingredients:
1 1/2 cups grated carrots
1 cup grated zucchini
2 cups all-purpose flour
1 1/2 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
1 teaspoon ground cinnamon
1/2 teaspoon ground nutmeg
1/2 cup vegetable oil
3/4 cup granulated sugar
3/4 cup brown sugar
3 large eggs
1 teaspoon vanilla extract
1/2 cup chopped walnuts (optional)