Ultimately, what I ended up doing was using canola oil to break up the zinc that was left over then I washed with Dawn dishwashing liquid. After that I rinsed his hair again a couple more times with white vinegar and then a light conditioner. On Saturday I will wash his hair again with a clarifying shampoo and then deep condition his hair. This has been quite an experience and I am going to make sure that we don't repeat it again!!