They weren't making guns for each other. FN first supplied the FN24 to Yugoslavia. They licensed Kragujevek Arsenal to produce the Yugo 24. I believe they may also have provided tooling. Just a supplier/customer relationship. The 48 was just a modified 24 and the commercial product was basically the same without thumb cutout and clip feed lips - an easy modification of the military action.Well, could be. I have never heard nor seen any reference linking in any way FN to Zas so thats news to me. I am aware of the mil version M48 and that they were a little shorter than normal, but that was a mil action with a thumb cut.
On the one hand you tell me nobody said they were in business together, but it sure sounds like they were if they were making guns for each other doesnt it?