more Anton Zak: http://www.friedhoefewien.at/grabsuche_de?submit=true&na...
if he is the one you stated so you can ask with his burial-date and cemetery at:
Historic registration records (1904-1975) - Informationhttp://www.wien.gv.at/amtshelfer/kultur/archiv/forschung/his...
E-Mail-adress at "Zuständige Stelle" - it´s free and you can get some info more about his adress, if he moved, married and other people who lived in same household, maybe all the children and so on.
phonebook shows 392 Zak in Austria and MANY Zak in Vienna!
Lower Austria (68)
Upper Austria (30)
Carinthia (6) http://www.herold.at/en/telefonbuch/zak/