* zebrasrv
 must run on the same machine as apache ? (in this case, opac and intranet cannot be separated)
 Or
***
<listen id="biblioserver" >unix:__ZEBRA_RUN_DIR__/bibliosocket</listen>
<listen id="authorityserver" >unix:__ZEBRA_RUN_DIR__/authoritysocket</listen>
***
 can be changed to point to another machine ?

Yes, Zebra can be configured to run a separate system for both biblioserver and authorityserver.  The koha-conf.xml file has an explanatory note:
<!-- [scheme:]host[:port][/databaseName] -->
<!-- scheme: tcp, ssl, unix, http, sru -->

I didn't realize you can even use ssl.  That's rather cool.  Anyway, you might have configuration like:

<listen id="biblioserver" >tcp:index1.liblime.com:2060</listen>
<listen id="authorityserver" >tcp:index2.liblime.com:2061</listen>

Since the default is unix socket, I'm not sure what the port numbers should generally be.
 
  Started with misc/bin/koha-zebra-ctl.sh ?

Correct.

--Joe