Hi Natalie,
I am not particularly familiar with the people you mentioned, however I have general background information. I believe that that there may have been a first generation of male Zwerdlings (between 1 and 4?) born circa 1750 who ended up in the Brody area. From the 1780s up to 1910s, Zwerdlings bit by bit left Brody for better opportunities elsewhere. I think Tarnopol was the very first place some Zwerdlings went to very early on. Because the surviving records are so incomplete, it requires a lot of effort to reconstruct the picture.
There is a Brody record of a Jacob Zwerdling who was either a first or second generation Zwerdling:
Jacob ZWERDLING
Death record
1831
Date of Death: 27-Jun-1831
Year of Registration of Death: 1831
Town of Record: Brody
House Number: 1191
Sex: M
Age: 40-60
This record comes from the Brody Jewish Deaths (1815-1861) database, fond 701, series 1, page(s) 146. The original records are held in Central State Historical Archives of Ukraine in Lviv (TsDIAL) and were added to this search engine on 10 July 2011. An image of this record can also be viewed on FamilySearch/LDS microfilm #2405310, item #9. The Gesher Galicia unique record ID is GG-BRODY-DEATHS-12732