I think I may possibly have made an error, but it is ambiguous. When I went on the English version of this zoo's website, it seemed as though the snow leopards were born at this zoo in 1989, making them the first ones born in that country, however the Google Translate version of the original site makes it look like that the zoo only acquired them (albeit as babies, as there is a picture of a zookeeper holding the cubs) in that year.... it still makes reference to the fact that the cubs were the first ever born in that country and I think it's unlikely that a zoo would acquire a sibling pair as cubs, the original facility would likely have kept them for a while and then split them up and matched them to unrelated animals in other zoos..... but it is possible and I'd hate for an error like that to mislead people unintentionally.
So to recap, this zoo either bred snow leopards for the first time in that country in 1989 as I had originally thought, or else acquired the first snow leopards born in that country in the same year.
My apologies again.