So I wasn't sure if this was intentional or not, but I found out 
can generate stacks with his Q off of Zz'rot Portal voidlings. If this is intentional, I don't really get how it's fair because you can just sit on an enemy Zz'rot and spam Q at the voidlings to rapidly generate extra ability power.
It's really not as good as it sounds because you are literally sitting around wasting time stacking Q while not doing anything on the map, pushing or anything. Zzrot minion don't give gold so you are only generating stacks.
If you are letting veigar stack Q off zzrot and not doing anything else on the map, you shouldn't be buying zzrot. Zzrot is for map pressuring one lane while you do something somewhere else on the map.
if he's doing that then go kill him.
Then maybe they shouldn't build Zz'rot when the enemy team has a Veigar? Or count on him farming stacks with it.
Nasus can do it as well and its just awful when it happens.
