Yeah, I looked into this a while ago forgenerating photo gallery zip files on the fly. Currently I'm using lazygal to generate static html galleries and if I want to give users the option to easoly download the full gallery, it basically doubles the size I need to store, as lazygal simply creates a zip file and puts it next to the photos and html files in the static gallery folder it generates.

So I looked to creating the zip files on the fly when requested & streaming them to the client onthe other end withou having to create temporary files and/or a lot of memmory consumption on the server. I got it working on a prototype and even found some articles from others that got it working - it is not that hard, really.