From what I've seen from CS
"Creatures that enter the zone or start their turns there take 1d10 + Intelligence modifier poison damage."
Creatures entering the zone means either they move into it, or a forced into it via forced movement, IE: they enter the zones space. If the zone enters your space, that is not the same as you entering the zones space. Hence if you move it on top of a creature it does not take damage... (at least until it starts it's turn in the zone).
Related.
Damaging spell effects do not count as hindering terrain, and so monsters do not get a saving throw to avoid forced movement into them. It makes no difference if it's a cloud of daggers or a wall of fire.