First, let's take a look at the hit. Gregor had committed to the hit when Zaitsev was still eligible to be hit, so in that sense, Gregor did nothing wrong. However, unfortunately, Zaitsev had toe-picked and was falling forward at the moment of contact. As a result, his head had hit the glass hard and left him shaken up on the ice and in need of some attention.
There was no penalty on the original hit and I doubt there will be any supplemental discipline either, as Zaitsev had been in the process of falling as the hit was being delivered, which is why the otherwise routine hit resulted in an unfortunate injury.