I have several Locations that have Zenworks. Each location is a different
tree. I want to merge the tress. Should I remove Zenworks from the source
server (source lan) before the merge? Or will it be OK to merge the trees
and Zenworks will merge along with the tree?

Each location has a full blown Zenworks for desktop Installed; Applications,
Inventory server (Root), Policies, Import Server, Image server etc....