You could find out a lot about these families by searching through the "Meldezettel" collections at the State and City Archives of Vienna. LDS has filmed these records (under the title "residency records" or "population cards"). The films comprise three major collections, each one vast in itself. The first challenge would be to pinpoint the film numbers that contain the sequences for your ancestral family names.
Apparently LDS is indexing one of these sets for on-line access. Only a miniscule portion of the records has been indexed so far. You could wait a bit, or get immersed in the films. The already indexed part can be searched by going to https://familysearch.org
, selecting continental Europe, Austria and "population cards" of Vienna. There are already one or two entries each when searching family names Zidek and Cermak.