Everything seemed to be ready for the switch. Old server called webmail.domain.fr (7.0.2), new one mail.domain.fr (8.0.2). This one supposed to become webmail.domain.fr. On this last one thx ZxBackup everything was up to date (user data, domain, GAL). I did install commercial certificate too for webmail... domain name.
What I did so far:
"Old" webmail unplugged, then zmsetservername....on new one as described in zimbra wiki, hosts...DNS record update on AD (A & MX), reboot.
Ping new "webmail.domain.fr" OK, however ldap error message about ldap services and also logswatch doesn't find webmail.domain.fr.
At this time I did have to plug back "old" webmail and new one went local.

I did also:
zmlocalconfig -e zimbra_server_hostname=zimbra.company.com
zmlocalconfig -e ldap_master_url=ldap://zimbra.company.com:389
zmlocalconfig -e ldap_url=ldap://zimbra.company.com
zmlocalconfig -e snmp_trap_host=zimbra.company.com
zmlocalconfig -e av_notify_user=admin@company.com
zmlocalconfig -e smtp_destination=admin@company.com
zmlocalconfig -e smtp_source=admin@company.com

manually updated new hostname in:

Other things from here:

1. As root - # mv /opt/zimbra/mailboxd/etc/keystore /root/keystore.old
2. As root - # /opt/zimbra/bin/zmcertmgr deploycrt self
3. As root - /opt/zimbra/libexec/zmfixperms --verbose --extended
4. Login as the zimbra and restart all of zimbra

Still problem about LDAP & Logswatch
Any idea would be appreciated!