What a strange thing to comment. The zoo are obviously aware and given the partitioning have taken steps to prevent it occurring while presumably investigation, as well as being by your own admission entirely open about the situation.
As
@FBBird has said, ZSL have held both species long enough that they know what they're doing. And the fact it took them so long to even attempt the mix goes to show they certainly calculated any risk.
Can't help but feel if it was any other collection this would be seen very differently to simply being "damning"...