Just a quick reply on the video part of ZenPhoto.
Personally I feel that video is only really possible/usable within ZenPhoto when one would be able to use a service like YouTube to store the videos. Leaving them on your own server would simply mean too much data to be transferred each time, and in case of lots of videos expensive in the end because of the money you would have to pay the provider for extra webspace and extra traffic.
Why isn't it possible, next to uploading your own thumb for the video, to add a field in the admin where one can add a custom link to the video (instead of the automatic image-link). In that field one could copy and paste the YouTube code that is also used in weblog posts to display the videos.
In my view (but I'm not a coder

), in the image.php there should be a second block of code, handling the insertion of the YouTube link given in the admin pages, instead of inserting the jpeg image.
All in all this would mean adding videos (actually only the link) manually, but what would be wrong with that?
Just my thoughts on this... And now I can hear the programmers thinking 'You stupid ***, don't you know that's impossible?' :=)