The space between the base and jungle is designed so that champions can't jump over it (Unless the ability is a global/almost global ultimate).
Zac's E allows him to, showing about a 100-unit miscalculation in its space.
I strongly believe this is completely intended.The jungle/base wall is like any other, and the way the game is programmed is that any leap over a wall will make it over if the leap goes over halfway to the other side. Rek'sai's tunnels can bridge this gap as well.
Lissandra and Rek'Sai can pass that wall too. I figured Riot intended that jump to only be hard/rare, not impossible.
