Having said I know nothing about ZEN on the Enterprise, I see this is Copyright Intelligent Software, written by MRL (of SET STATUS 42 fame!)
I also see but not noticed why MRL
Only the first "Notes on Enterprise version" pages are IS copyrighted, later the originaly Lynx manual attached.
Probably Martin Lea do the Enterprise adaptation? I guess if he got the original sources then about 2-3 day to do it!