So 4.5.6 > 4.5.11 > 5.0.2 is fine.
However, it looks like you'll need to switch operating system platforms as well (OpenSUSE 10.1 > 10.2)
Some notes have been posted to
MigrationFromEOL - Zimbra :: Wiki
In addition you may want to checkout:
/blog/archives/2007/10/moving_zcs_to_another_server.html
-Be sure to use the exact same zimbra version (4.5.11) when doing the platform switch, then upgrade to 5.0.2
4.5.11 FOSS:
Release Notes &
Downloads
5.0.2 FOSS:
Release Notes &
Downloads