Have both of these and SBR'd them. Decided to install 3X prism scopes on them as my eyes aren't what they used to be. Just bought two Gen 3 Master Mount bolt on side rails that attach to receiver.

I'm wondering what Optic mount works best for these with their dust cover mounted rear sight?

Ideally, I'd like optic to be centered over the bore.  

RS Regulate is definitely the best option

I've seen those and understand that they have different top sections depending on what rifle it is being used on. I don't know which one is appropriate for the ZPAP's

If you are worried about the rear sight interfering don’t be it’s so for forward it’ll be out of the way  with a rear biased prism mount

RS regulate lets you adjust it quite a bit too centering shouldn’t be an issue.

The top pieces plate basically universal, the bottom piece that attaches to the side rail is specific on the rail type.  Yugo/Zastava was a proprietary rail type but you just need whatever that Master mount is compatible with.