You can achiee this with filters. But you will have to code these things, they don't come for free. You should be familiar with PHP coding and a bit of the Zenphoto architecture, specifically the plugin architecture and the filter architeture.
Register user provides a hook to its form through the `register_user_form` and `register_user_registered` filters. The standard use of this filter is to integrate the register user fields with the comment form fields.
You should start by understanding how these work. Then you are free to make your own versions of these filters. I would suggest your best bet it to add the new fields you want to your version of the comment form plugin, but if you do not enable comments just provide the handling that form does for register user and for the admin tab.