This is an excellent idea! Much like transdermal Magnesium, which of course is what Epsom Salts
do for you in a bath.
You could try making your own transdermal Zn supplement with DMSO and applying that topically. DMSO carries in small molecules, anything under 1000 daltons molecular weight.
It's been done with Vit B12, Mercola reported on this years ago and many have made their own transdermal preparations with herbs, drugs, vitamins etc. Check out the DMSO list on Yahoo for more information.
I own the DMSO Yahoo list:
Also the new Pyrroluria List on Yahoo: