Preheat oven to 365°F.
Line a 9x13 pan with parchment paper. Lightly butter (or spray with baking spray).
In a bowl combine flour, cinnamon, baking soda, and baking powder; set aside.
In a large bowl, on medium speed, beat sugar and eggs about 2 minutes.
With a fork mash the bananas. Grate zucchini. Add bananas, zucchini, oil, and vanilla to sugar/egg bowl. Give it a quick mix.
Add half of the flour mixture and mix; add remaining flour and mix.
Pour batter into a pan. Bake in a preheated oven at 365°F for 17-20 min. Check readiness with a toothpick, it will come out clean if ready.
Completely cool cake.
Beat cream cheese and powdered sugar until creamy. Spread cream cheese layer over the cake.
Take melted chocolate and place it into a Ziploc bag, snip off the edge. Make a few lines atop the cream cheese layer with the chocolate. Take a toothpick and make swirls with the chocolate. Refrigerate for an hour. These are absolutely amazingly delicious if enjoyed fresh, meaning the same day.