as salam alaikum
there are three major opinions as far as the place of burial of Sayyidah Zaynab, peace be upon her: Madinah, Damascus and Cairo. Different scholars tried to bring evidences in favor and against each one of them. It is very difficult to bring a definitive proof for any of them. The scholars have also differed as to the "strongest probability" may be, it is therefore appropriate to be cautious in judgment even after having analyzed the various sources.
With prayers for your success.