A fair adjustment to increase Zac viability in Diamond and above
Zac is a champion that relies on successfully landing an elastic slingshot to have an impact in teamfights. I notice that at the highest ELO's of League of Legends, Zac struggles because it is really hard to land it due to the fact that the Shadow it produces is too obvious and telegraphs the ability. Either all critical targets leave the area before you land, or someone knocks you out of Elastic Slingshot. I am no longer surprised when an Alistar groundslam or Thresh flay knocks me out of Elastic Slingshot. Before reaching Diamond, I was almost never knocked out of Elastic Slingshot (maybe one out of 10 games).
I would like to see Zac back in Pro level play, so I think a fair suggestion would be to give Zac the Malzahar treatment. Malzahar was given a passive that would allow him to get his ultimate off without instantly getting stunned out of it. I suggest that Zac be immune to knockups while using Elastic Slingshot. It would not impact Elo's below platinum, and make a lot of sense as it is unrealistic to imagine this massive pile of goo flying through the air only to be stopped by alistar smashing the ground. I feel like this adjustmant still allows a lot of counterplay (since you usually have over a second from the moment the shadow appears to when Zac lands) and would bring back viability to Leagues most flexible champion at the highest ELO's, without impacting him at lower ELO's. Who doesn't want to see Zac back in the LCS?