Preheat the oven to 350 degrees.
In a large bowl, prepare cake batter per box instructions. Then, fold in shredded zucchini until the cake batter and zucchini shreds are fully mixed.
Line a 13×9 sheet pan with parchment paper. Pour the batter into the pan and bake for about 15 minutes or until a toothpick comes out clean.
Let the carrot cake cool completely. This is an important step because you don’t want the icing to melt when you put it on the cake.
Once the carrot cake has cooled, slice it into 8-10 bars.
Pipe a border of frosting around each bar then pipe frosting in the middle and smooth out
Using the orange cookie frosting, drizzle on the icing to make a carrot shape. Then, use the green cookie frosting to create the leaves of the carrot.
Once you have the carrot cake zucchini bars decorated, you can serve them or place them in the fridge so that the icing can set further.