All in all you just need the right angle and minimal line of sight. Not as if you need to completely circle the creature, so a move action will do.
And only one of them really hits Claudia, that natural twenty. The rest of the zombies simply don't have the hit bonus they need.
Which reminds me.
Raineh, look me up the AC on that dinosaur.
Also.
Rolled 1d20 : 19, total 19