Dagar,
See
/blog/archives/2007/10/moving_zcs_to_another_server.html
Use the SAME zimbra version during the actual platform switch.
With your setup whatever you choose to do first -platform or ZCS switch- looks to be ok.
Mrich,
Are you NE or FOSS?
You will need this process:
LDAP Replicas 4.5.x > 5.0.x
All:
http://www.zimbra.com/forums/announc...r-profile.html