In-place update NW 6 to NW 6.5 with ZEN 4.01

We currently had our old school-server upgraded (hardware). Now we
aren't sure whether it is possible to upgrade our server software, too.
Right now, the server in question is running netware 6.0, groupwise 6.5,
zenworks 4.01 and bordermanager 3.7 (yes, all on one server - it's just
for 400 users), latest patches and service packs installed.
We've got the license for nw 6.5 and bm 3.8, the only question remaining
is zenworks 4.01. Our users are relying on groupwise and netstorage for
access from the outside of our net. Zenworks is used for application
deployment, imaging and inventory. Can we still install zw 4.01 on nw
6.5 without the middle tier server or does this affect any of the
mentioned services? Do we have to reinstall zenworks after upgrading to
nw 6.5 and bm 3.8 or can we just disable/uninstall the middle tier server?

Thanks for any help!