So storage replication only works between nodes of a cluster, zsync between any hosts as long as the requirements are met (so it doesn't even have to be PVE node):
System requirements
Both, target and source server must support ZFS (best practice: use Proxmox VE hosts).
SSH must be installed and configured
to receive email-notifications, a working mail server is required (e.g. postfix).
cstream
perl
scp
JASON.pm (libjson-perl this is the Debian package name, e.g. needed on Wheezy)