I followed this link
[SOLVED] Zimbra Migration Strategy thanks to Sir Bob.
then i copied the /etc/samba folder to the new server with all *.tdb files.
then edited /etc/ldap.conf to the required settings then imported samba and nis schema
chown -R zimbra:zimbra /opt/zimbra
/opt/zimbra/libexec/zmfixperms
import posix amd samba
cp /usr/share/doc/samba-3.0.28/LDAP/samba.schema /opt/zimbra/openldap/etc/openldap/schema/
add nis.schema and samba.schema to /opt/zimbra/conf/slapd.conf.in
include "/opt/zimbra/openldap/etc/openldap/schema/nis.schema"
include "/opt/zimbra/openldap/etc/openldap/schema/samba.schema"
#indexes for PAM
index uidNumber eq
index gidNumber eq
index memberUID eq
#indexes for Samba
index sambaSID eq
index sambaPrimaryGroupSID eq
index sambaDomainName eq
then restart zimbra