Thinking it twice..
- If you want YOUR creatures turn into zombies to multiply them, so why would the spell deal damage? Turning an opponent's creature into a 2/3 damage zombie isn't specially good so the spell would be casted only in your creatures.
- If you want to use the zombies as CC, you should have zombies first, so you would just use zombies instead of the spell.
In conclussion, the spell dealing damage is useless. Also if the zombies deal 2 damage instead of 1 it would be good against rushes maybe, but now they are pretty much useless