I see you have lost all of the timestamps information.
It' s normally not possible to preserve the time stamp when you transfer over serial cable, however, a number of the non-factory original disks were indexed with a disk cataloging program that time/date stamped each file. Look for a .DID text file in each zip file. Here's an example from the Autodex-80 zip file:
--AXID.DID --AXID.DID 041883 Code to identify the contents of the disk
--AXID.DID AX.COM 041883 AUTODEX
--AXID.DID FINETUNE.COM 041883 Options for AUTODEX
--AXID.DID INSTALL.COM 041883 Install AUTODEX from B: to A:
--AXID.DID TERMDEF.COM 041883 Terminal Definition (Not normally used)
--AXID.DID TERMDEF.TXT 041883 Notes on TERMDEF
I plan to ImageDisk some of the system disks which will preserve the time stamps as well. The Concurrent CP/M system disks are first on my list. I will either need to get out my old PC rig for doing this or (and this seems much more exciting) see if I can get a recently acquired Gemini Board working in the Z-100 and use ImageDisk from there. The Gemini Board promises much better IBM PC compatibility but I'm not sure how much that compatibility will extend to low-level disk drive access.
And I need to give special thanks to Bill Adney. It was his system and software I acquired over the summer and he took immaculate care of his equipment including indexing all of his floppies. I only ran into one disk I wasn't able to archive.