If I understand this correctly, you have been told the following,
which may or may not be true:
1. Your ggf is Zalman Vevel SHAPIRO, but his surname may be Getzel,
even though that is normally a given name.
2. He probably died before 1900. He does not appear in the 1900 census,
and there are few records extant >from the 1890 census.
3. He is reportedly buried in Gomel Khesed Cemetery on the Newark/
Elizabeth border. That cemetery actually appears to be a landsmanschaft
of what is alternatively know as McClellan or Mt Olivet cemeteries after
the closest intersection.
I think you need someone to look at the tombstone and the cemetery
records, and someone to check out the death certificate, which is probably
in the archives in Trenton NJ. Perhaps a Gener in each of those areas
will volunteer to do that for you once the weather improves.
By the way, I would be suspicious of the proposition that his wife
immigrated in 1897, more than a dozen years after her sons came to the U.S.
San Diego CA