> If a place name is guzhu, how to denote its people or language,
> guzhuan or guzhunese?
Persistent? Since there is no established term and Guzhu is not as
familiar a place-name to westerners as, for example, Hong Kong, I
would suggest a phrase: the people of Guzhu; the language (dialect) of
Guzhu.
If you insist on one word, I would suggest "Guzhuese". It gives the
clearest indication of what the place-name actually is.