One can't always rely on the NYC marriage OR birth records being complete in Ancestry as the NYC vital records aren't always complete..
The records after the marriage were supposed to be returned to the NYC records authorities, but that did not always happen. I know of very early Brooklyn marriages that are not in NYC files as the church wedding was never reported to the vital records offices. I also have an uncle whose first marriage is not recorded and then in 1939 and 1942, he may never have actually gotten married after getting licenses. Stevenmorse.org is often a good bet for finding elusive data.. I prefer to use Gemangenealogygroup.org rather than Italian. The German and Italian groups collaborated in creating the databases they use, but they are only as good as the records that went it (discounting for spelling errors). In the past two years, Italiangenealogygroup changed (updated) their front end user interface. While some of the new changes are good, like searching a name in ALL their databases at once, the ability to sort the records by clicking the column headers in the returned lists was lost; so I prefer the genrmangenealogygroup site.
Marriage license questionnaires are maintained by the NYC Archives and usually are three pages of data, but require someone to search for them. However, if they married in NJ, that will not result in finding a record, either.
I did not find a marriage for Frank Zimmer in familysearch.org nor in the NJ Ancestry marraige records.. I did locate the probable marraige of a daughter of Sarah and Frank, Lillian Kaplan, in April 1928 to Murray Dravich.
Good luck with your search.