For the chocolate rice pudding, add the uncooked rice, milk, and sugar to a pot over medium heat, stir to combine, and cook for 20 minutes. Add the chopped chocolate to the rice pudding in the pot and stir until it has completely melted.
Spoon the chocolate rice pudding into a round 12-inch cake pan and push the bottom of a slightly smaller pot into the rice pudding to create a well. Transfer the cake pan with the pot to a preheated oven and cook at 350°F for 20 minutes. Remove the pot from the cake pan and let the chocolate rice pudding cake cool for 1 hour.
For the zebra cake filling, add the uncooked rice, milk, and sugar to a pot over medium heat, stir to combine, and cook for 20 minutes. Meanwhile, combine the unflavored gelatin powder and the hot water and stir until the gelatin has completely dissolved. Pour the cooked rice pudding, dissolved gelatin powder, and coconut milk into a blender and puree the rice pudding mixture until smooth.
Divide the rice pudding mixture in half. Add half of the rice pudding mixture to a blender, along with the cherry puree, and blend until combined.
Alternate pouring small portions of the white zebra cake filling and the pink zebra cake filling into the chocolate rice pudding cake, starting with the white zebra cake filling.
Refrigerate the rice pudding zebra cake for 3 hours before serving.