Hello: I customized the functions.php located in zp-core folder. Minor cosmetic customization.

Now I get the message "Zenphoto has detected a change in your installation" The script functions.php has changed.

Please advice on how to disable this message, or make ZenPhoto understand the change is allowed.

Thanks.

It's a security reason.
See here : http://www.zenphoto.org/news/installation-and-upgrading

Thanks; I am aware it is a security feature; but, how do you turn it off?

You cannot. Just do what the message says and it will go away.

As a general rule anyway: Never modify core files. Use plugins or theme based custom functions if you need anything else or your are "on your own".

Only an administrator will see that message and it is really important that he does see it to take action on the issue revealed.

Thanks