For some reason I thought that
Javier was "hah-vee-AIR" and
Xavier was always "ex-zavier" or "Zay-vier."
If you check the description in this database it comes from the Basque place name Etxaberri meaning "the new house". I think Ex-Zay-vier would be a more authentic pronunciation of that.
Anyway, my co-worker's last name begins with Z, so I kind of hope they are not going with the "Zayvier" pronunciation. I read it in an email so far and haven't asked.