Generally the Zastava rifles that were imported as kits and any early imports did not have optics rails.
The recent imported PAP rifles have rails.
They are attached in a non standard set back which somewhat limits the scope mounts that can be used.
The answers is that Zastava specific rails are very uncommon and if installed in the PAP location they require specific mounts.
Other combloc rail types can be used but require mocking up to see how they lay out on the receiver.
Retrofit rails on Zastava rifles is not very common.
There are non rivet rails that may fit or the Texas Weapons System receiver cover types.