Misfits punished Zen with Zen + Tracer + Genji + Widow + Lucio etc. The comp they made is really good at that. That works less effectively against Ana, Zen himself loses to Ana in a lot of ways.
Like, think of it this way. People already know Zen counters, they are getting better at them , and Ana plays a good part in fighting him. Ana counters are flimsy atm, people are getting better with her specialized comps, etc.
So it's very likely that as western teams get better at Ana/tank set ups that Zenyatta declines. It's not impossible for some Zenyatta lord god like Custa to hold out and make it work for a bit, just extremely unlikely unless some major breakthrough happens relatively soon.
Also yeah, Chips is hands down the best Ana player in the world by a pretty ridiculous margin. Ryujehong and Zappis aren't slouches either, but the gaps in skill level between the different top Anas are pretty apparent.