757 crew never stated that they are in TCAS descend.
and as far as same level - both aircraft were cleared to FL360. so he should have put more attention to them.
but generaly - I'm working in relatively small ACC unit, but nobody would allow such degradation of service without backup. I think Zurich controllers accepted what the managment threw at them and result was a tragedy.
and I'm not blaming the atco, I just wanted to emphesase, that he had a responsibility and he failed to use all the resorces he had in order to prevent the collision (ultimately).