May I add a suggestion for another reason for clan purposes?
Actually Using the Regular Zombie Panic Purpose or Gameplay
A 50/50 match(like clan battles, I guess, anyways) but for the reg Zombie Panic or Zombie Panic objectives. Just give the match a certain name to imply a different viewpoint on regular matches (which I personally and honestly already enjoy thinking about and imagining.)
The only difference is scoring. Maybe if the scoring is different enough, we'll have a score-keeper.
Each team (sometimes 3 maybe not 4 for exreme different teams for BIG tournaments requiring the best of the clan) must work together to survive the longest. All or both teams also have to work together and maybe there will be judges who will continuously take notes on how well certain players are working (which may be hard since ZP wasn't designed for easy observations esp. concerning clans and player names. If there are ever judges, they should only be honest and must know the quote: a truly-good and most skillful clan is honest, especially the judge.)
Generally (Minor Clan Represenations provides by choice of any clan member and group idea & Gameply)
So while in the game [Subway at the best choice for big matches and on hopefully a good server(for my and few other's slow ..arse CPUs.)] Clans, lol, could eventually have or keep the reg skin's body or face but adds a clan jacket or some kind of representation agreed upon by the clan, if anyone wants to go that extreme.
So in the game, clans may separate or their tactic is to stick with the other clan but in a certain form but to also help (which can add points, maybe, or it's strictly to obliverate the other clan) They must carry out the objectives or kill off everyone living but all the points would be based on how well each clan performs. It can be performed after agreement on whether each clan must kill themselves when some turn into zombies (so cheating can be a matter) or a personal clan's zombies can stick with the clan itself. The hardship is distinction, whcih probably involves also ZPA.
I haven't really played ZPA yet and I'm hoping my account is enabled to have a chance so I know whether or not to support my idea or not because so far, it seems possible, if not kind of likely.
One More Thing
I mean, I enjoy thinking of the fact of a weird, fancy scoring system where even in the end of the round where pressure is applied to the last person standing of not just having all eyes upon the one who, I think points should be given for, running away as last person standing. Example: 1 point may be given every 30 seconds and 3 for every zombie killed. That way, the player is encouraged to shoot more than run.