recently my local rsync and my remote rsync failed talking to each other properly

This is the message I faced:

rsync: This rsync lacks old-style --compress due to its external zlib. Try -zz.

Using “-zz” instead of “–compress” does not always help. Today my local (OS X El Capitan) proved to be too old. I installed Fink’s rsync, now it’s fine again.

• http://finkproject.org

Actually:

• there is not just one local rsync (OS X …, cygwin),
• and there is not just one remote rsync (on my Synology NASs: optware, optware-ng, entware-ng).