[comp.os.cpm] What does 'z' in a file extension mean?

Ralph.Hyre@IUS2.CS.CMU.EDU.UUCP (03/12/87)

Is it some more elaborate form of data compression?
If so, I don't see a reference to it in the <cpm.starter-kit>
directory.

For example, I have files named read.mz! and pcpi/z3d.zc.
I'll be very grateful of someone could answer ASAP.  Thanks.

					- Ralph Hyre