Can you combine boxes and armor on horses in Minecraft?

I was wondering if you can combine boxes and armor in Minecraft for horses and if so how does that work?

A lama can carry boxes that fit 3, 6, 9, 12, 15 items. A horse can't transport anything.

No, I know that you can "combine" donkey and horse and then you get a mule but this can only carry a box and a saddle like a donkey and a horse has horse armor and there's a way to combine both armor and Boxes?