I suggested ZIP simply because it's so widely supported, it's built into the stdlibs of many higher level languages and most operating systems have GUI tools to

I suggested ZIP simply because it's so widely supported, it's built into the stdlibs of many higher level languages and most operating systems have GUI tools to browse the contents. I don't know of any other containers that are as widely supported, but I am all ears. If it's a container that requires the recipient install 3rd party tools, then we may as well skip that part of the proposal entirely.