Update .. I did a little test, by installing ZenPhoto 1.4.1.6 in a subdirectory via simplescripts (I know it's bad, but quicker than uploading via FTP on my slow provider).
The simplescripts test install with the older ZenPhoto DID have to option to enable imagick, so it IS supported by my server, just not appearing on my current install.
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PROBLEM SOLVED: Hope it helps others in the future: All I had to do was go into my cpanel PHP Configuration (via Bluehost) and change the PHP version from
"PHP 5.3" to
"PHP 5.3 (Single php.ini)"
This basically makes all subdirectories use the main /public_html/php.ini file. Seems to do the trick for ZenPhoto. Before I had copied the php.ini from my main root to the subdirectory where ZenPhoto resided.
PS - My zenphoto installation is on a subdirectory on my main host that is redirected to a separate domain I own.