Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch pan.
In a medium bowl, stir together the flour, baking powder, baking soda, cinnamon, salt and nutmeg. Set aside.
In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the eggs one at a time, then stir in the vanilla. Gradually stir the dry ingredients into the creamed mixture. Finally, stir in the carrots, zucchini and walnuts.
Spread the batter into the prepared pan.
Bake for 40 to 45 minutes in the preheated oven, or until a knife inserted into the center of the cake comes out clean.
Interesting Facts
Carrots and zucchini add moisture and flavor to this cake.
Adding chopped walnuts is optional, but adds a nice crunch.
The cake is best served warm with a scoop of ice cream.