Nidalee able to kill Zed during Death Mark

During a few different online games and custom games where friends and I tested this 'bug', we found that Nidalee was able to kill Zed while he was ulting her. It happens most often when Nidalee uses her E while in cougar form. Right after Zed ults, if Nidalee happens to use her E, Zed dies and his ult doesn't go on cooldown. We tested it on a Lan connection to ensure it wasn't a latency related bug and found that it still happened?

Anyone reading this should try it themselves and see if it also happens, I'm still unsure if it's an actual bug or just really good timing.