Hello,
Its my understanding that the Zen personal web space that you get with your account is itself actually a sub domain off Zen's own Primary domain. (you might want to confirm this with Zen) if I am correct on this point. However unless your web space if fixed permanently in some way to your account then as a sub domain it should be fairly flexible, in terms that the name of the sub domain it can be changed to whatever you want to call it.
**The analogue is abit like with email address's i.e. anything after the @symbol.co.uk cannot easily be changed once created (well not without major hassles) but you can easily change whatever appears infront or before the @ symbol of the address.
**So if the primary domain is say :- "zoom.co.uk" and then you have a sub domain called "sports.zoom.co.uk" the sports part could be changed for say sales thus "sales.zoom.co.uk" etc. Sub domains are more easily changed if I am correct.
**A quick email or phone call should be able to confirm this.
Ivan