The sad thing about checking links is finding abandoned projects, like the 24 Hour Zine Thing.
The 24 Hour Zine Challenge asks zinesters to create a 24-page zine from conception to final product in 24 hours straight. Zines should be of suitable size and technical difficulty so that this truly is a challenge for individual zinesters.
Zine Thing Link Rot:
I also found 24 Hour Comics Day, which started the idea for the zine publishers.
Cartoonists around the world will face the 24 hour comics challenge. To help these cartoonists, some comic book stores, educational institutions, libraries, businesses, and comics clubs will host special 24 Hour Comics Day events. They'll provide cartoonists with a space to work, access to food and drink, and camaraderie.
Both projects have been abandoned. I'm posting the link for history and reference. Maybe someone will come along and work on the project again, or start up something like it.