"El e casier, ea e economistă."

ambiguous, when you have to chose between ”casieri”, ”casier” and ”casierul”, last two forms are both grammatically correct, as the two clauses are independent, and both expressions (with or without article) are common ”El e profesorul, ea este femeie de servici”. ”El e doctorul, ea este asistentă”. The two clauses are not dependent, they do not need to put their articles into accord.