I just started using ZP and I love it!
For my personal stuff its perfect... but I have several web clients in the nightclub industry that have some specific needs.

Here is what I need and maybe some on can tell me if its possible:

1. Protect after thumbnail.
   I want a gallery that allows people to view the thumbnails but when they want to see the bigger picture they are prompted for a password.

2. User Registration.
   I do not want want to add every user manually. We get almost 1000 people a day going to our site and I need them to be able to sign them selves up.

Now if these functions are not in ZP by default is there a Hack or work around?
I had one idea that I wanted to get some feedback on: Can have ZP as a page inside of a CMS like Joomla and then somehow protect access to the pages on the other side of the thumbnails? Then I could just let the CMS handle the user management.
I am familiar with Joomla but not WordPress... if it can be done in WordPress I dont mind using it... I just NEED this functionality.

Well, with enough coding knowledge virtually everything is possible to hack...:-)

1. I have not tried this but you could probably use the zp_loggedin()-function for that, so that only logged in visitors can see that.

2. There are no plans to add that. Actually Zenphoto is not really meant for such a purpose. You can add a feature request ticket of course, but we can't promise anything, since our resources are limited.

To your CMS question, I don't know of anything regarding that. There has been a hack of a combine log in for Wordpress and Zenphoto, but that was for older Wordpress and Zenphoto versions. See our extensions page for the available hacks.