Tried the "curl" import.
What a pain.
Curl is not in the path on appliance 22.214.171.1246 so had to use :
sudo find / -name curl -print|more to locate it
rephrased command line with full path to curl...
sudo /path/curl -k -u admin:PASSWORD --data-binary @/path/to/USER-account.tgz https://MAILSTORE-FQDN:7071/service/home/USER@DOMAIN/?fmt=tgz&resolve=skip
and got the response
curl option --data-binary out of memory.
Now shutting down domain controller and firewall VM's so can allocate all the memory on the box to the mail server for the duration of the import....
Maybe an import facility that worked would be a valuable addition to zimbra - perhaps a documented one would be even better.
Will advise results.