There is something called topic evolution. Anyway, it is a title.
We dont say Queen Windsor (the Queen's last name). But we do say the Queen of England. It is most likely a title.
Zeal was probably created quite a while before the queen came around, Judging by all te libraries and research that had been compiled.
Most empires arent named after thier leaders. The closest thing we have to that is Alexander the great naming various cities and camps after himself, calling them Alexandria or Alexandretta.
We dont, however, call his empire Alexandria, we do call it the Alexandrian empire, but that is because he himself was the driving force behind the conquering of all the lands. Rome had the roman empire, but if Julius had conquered it all, it would have been the Julian empire.
Queen Zeal is just a title, nothing more, nothing less.
EDIT: Drawing the parrallel that it must be the last name because the emperor was refered to with his last name and that CT was made in japan and that japan was once part of china is just silly. The queen in english is refered to by first name becasue it is a status symbol (THE king Edward); the royal family wanted to be differentiated from the masses who were identified primarily by last name (Mr Biggs, Ms Firth.). you really are being a bit silly here.