Lady, EVOLVED 
somebody in the Austin Group standardize zip pls
so many formats these days are just specially-engineered zip files and there is no Posix way of engaging with them
@Lady Most (iirc by far by far) zipformats are internally XML-based. (Potentially some are JSON-based? Not sure/don't remember. Someone should start a wiki.)
Are there POSIX XML capabities?
Even if you could POSIX zip/unzip them for the structured-plaintext files, how much would you be able to POSIX do with that?
Or am I missing something?
@gaditb there aren’t POSIX XML capabilities, but i’d draw a distinction between content creation and content packaging. i think it’s reasonable to allow OS‐specific tools for content creation while expecting content packaging to be portable across OS’s. (i also would love if XML were POSIX, namely the core functionality of xmllint and xsltproc, but that’s never going to happen.)
@gaditb (i will probably just require libzip)
@gaditb but the shorter version here is that i’ve already resigned myself to requiring libxml2 and libxslt, which are widely‐available if not POSIX, but don’t want to have to choose between Info-Zip, libzip, and libarchive, and would rather if pax just had a zip format added instead