Spring Garden Cake
Prepare carrot and zucchini cakes as directed, and cool to room temperature. If necessary, use a serrated knife to trim cake tops level. Each cake should be about 1 1/4 inches high.
Prepare cream cheese frosting. Place zucchini cake on a 10-inch cake round, and spread top of cake with 1 1/4 cups cream cheese frosting. Place a carrot cake on top of the frosted zucchini cake. Chill until icing is set, about 15 minutes. Ice entire cake with remaining frosting. Chill until firm, about 30 minutes. This can be done up to 1 day in advance.
Sprinkle top of cake with 1/2 cup cookie crumbs, leaving a 1/4-inch border around perimeter of cake. Using a paring knife, lightly mark cake top, dividing into quarters or four "plots." Rake the plots with the tines of a fork. Place green sprinkles on the perimeter of cake. Arrange marzipan fruits and vegetables on the plots. Carefully press pastillage fence posts onto the side of the cake, about 1/4 inch apart, and place candy pebbles around the base of the fence. Serve cake at room temperature.