The z-push-combined package contains a special data backend provider
for Z-Push to combine several data backend providers. This allows to
handle each type of item (e-mails, contacts, calendar entries, tasks)
by a different backend. A combination could be to handle e-mails via
the IMAP data backend provider, while all other items are handled by
the Zarafa data backend provider. If you want to use this, you will
need to install this package and additionally the other Z-Push data
backend providers that shall be combined.