Right now, the knockback for being shot, for no better words, sucks. You don't even need SMGs, or a lot of people shooting at you [or worse, a lot of people shooting at you with high powered guns] to be crippled - as in, can't move, can't use any special abilities.
Aside from being utterly unrealistic, it makes the game unbalanced as fuck. Yes, I know regular zombies deal a lot of damage, but not all that are zombies are regular zombies [still have fastie, poison crab, headcrab, fast crab, wraith, poison zombie, and chem zombie to look at, plus it is REALLY easy to dodge.
If you reduce it, or better, remove it, it would be better - people won't want to quit when picked as zombies, and spawncamping - while not solved - would be complained about less since people could actually DO something about it EASILY as zombie.
I mean, really, wouldn't you feel more encouraged to fight if, when faced with a couple of people sitting outside of the spawn with Owens, or Fagnums, instead of being paralyzed and unable to move at all or use special abilities you were able to keep moving?
I know at least one or two may reply about it being in the source engine, but I really don't know - I mean, in TTT if you get shot with an AK or H.U.G.E, you don't get crippled, unable to shoot or move, so if IT IS, then it has to be ADJUSTABLE - otherwise, it has to be something in ZS if not in the engine.
tl;dr: Knockback in ZS is too crippling, a lot of complaints regarding things like camping would be reduced by reducing the knockback if not removing it.
EDITED to fix typos, make more sense. Note to self: don't type without your glasses on.