Displays Images (JPG), the corresponding Exif (if available) and provides zoom functionality (based on Lightbox).
This is most likely due to the fact that your web server is not running on PHP 5, which we need for PEL.
Basically because there is no other plug-in which is able to provide access to all Exif tags (f.e. the image number provided by Nikons D200). If you ask me, most existing plug ins only provide a rudimentary implementation. Apart from that, none of them includes an elegant lightbox-style way of zooming pictures. All in all that was reason enough to write ExZo.