All Bib Record updates for fields other than local fields should be done in OCLC and re-exported into the NZ (or the IZ for local-managed Bib Records). Note that NZ bib records are regularly updated via an import profile when content changes for SUNY-held titles in OCLC. If you find that a change made in OCLC isn't showing on an NZ bib record, feel free to re-export the record.
You may see this message on an updated Bib Record: "An external process has changed the original record."