Usually the -0 option. https://linux.die.net/man/1/zip -mx=0 for 7zip style programs.

If you also used the mt option with 7zip and just stored you probably could have a decent read rate as I think it spins extra threads.

Yes, but I don't think anyone does that.

This ability is an important aspect of “document” archives following the open container format (OCF): the first file in the archive must be uncompressed, called “mimetypes”, and contain the mimetype of the document encoded in us-ascii.