As far as I know, Dazhiarn is just an alternative way of spelling. (Seem to vaguely remember it being used in the Legends of Lone Wolf novels.) Daziarn seems more common, though.
Maybe the former spelling can be thought of as an archaic version of the latter one ... (Just food for thought, as nothing like that is alluded anywhere. Looks somewhat archaic, that's all.)
Paido