It's pretty easy to make your own Zinc Oxide Ointments, and for a heck of a lot cheaper. I somewhat recently bought a lb of micro Zinc Oxide for about 8 dollars. Micro meaning small enough particles to rub in clear, but not technically nano and less chance of possibly getting into the blood stream. Anyways, as i look like a "stereotypical" Scot (reddish beard and all), i burn very easy. That lb of Zinc will last quite a long time and make a lot of sunscreen.
Re: the nano and possible health issues, what i rarely see mentioned is the possible importance of the carrier medium. If the Zinc gets suspended in a heavier and larger moleculed type oil or cream, it's less likely to penetrate through the deeper layers of the skin because the carrier medium itself is going to more or less sit on top of the skin or first couple of layers.
In other words, DON'T put micro or especially nano Zinc particles in carrier oils like Emu, Macadamia, or Jojoba oils because these are deeply penetrating oils that can get very deep into the skin.
Btw, for sunscreen, i mix the Zinc into Sesame and Shea Butter since these also have some minor sun protecting properties.