As I have both games I did a size comparison of the miniatures figures in order to see if I can use Last Night on Earth heroes as Zombicide additional survivors.
There is a 2mm difference in height - something you will not notice while gaming. The negative point is that LNoE heroes are made of grey plastic like the Zombicide zombies.
I now have to do some extra character sheets for Zombicide and may be paint all those minis.