Ook, u like loosing double transaction (BTC's bites!) + exchange fee? 10-20%? Now I'm testing the pool with 0% fee, immediate payout of confirmed crypto (if u mined it - u get. no exchange, only if u want to) and double hashrate vs zpool's. Scrypt only, it limits, for sure, but: ~110-120% daily net revenue at rented hashpower w/pool's autoswitch (sometimes it sucks), ~130-140% w/manual coin switching (I get real-time almost precise data) vs no breakdown (!!!) at zpool. Yep, I get pain in the ass selling alts twice a day in complicated ways, but this pays, only 1-2% transactions losses maximum (profit sometimes!), including BTC transfer to NH. And I hope my bot in development is ready and operational in 2-3 weeks.
Right if you want to mine a specific coin then you should mine on a pool that directly pays you that coin. That makes the most sense because then you don't have any risk of the price fluctuating and losing value in trades. That's not how Zpool appears to operate. But that doesn't mean that Zpool is stealing anything. It would be no different than if you mined on your 0% fee pool and the coins price dropped 20% before you could sell it out. Except you're paying the transfer fees too and from the exchanges and you have to put in the labor to make sure the trades happen properly. You get more control, but you have just as much risk in losing or gaining value.
If you don't like Zpool then don't mine on it, but it doesn't make any sense why you come here to complain that the pool should operate the way that you want it to operate. If you can make more on another pool no one here or anywhere else is stopping you or trying to convince you not to do that. Fact is if you run a Multi-algo switching miner and want someone to auto-exchange coins to BTC for you then Zpool is the best pool to mine that I've found.
If you want to sell your own coins and mine each coin directly then there are lots of pools out there that will pay you out directly and allow you to exchange them yourself. You're asking the pool to operate in a way that it wasn't designed to operate. I admit this information is not clearly spelled out anywhere on the pool site, but once you understand how it operates then it makes sense. Could you make more somewhere else? I bet you likely could, but you won't do it with as little effort as Zpool makes it.
Personally I haven't had any issues getting my payouts in either BTC or DGB, but I noticed that when I mined for DGB I could make more just mining it directly on something like Suprnova or theblocksfactory. It wasn't 20% less and it could actually be potentially more than I could mine DGB directly depending on the values of other coins. If you are mining a single algorithm and don't want to switch between all the coins that algorithm could potentially mine to maximize profits then again Zpool might be better and certainly would be more convenient than having to exchange all those different coins yourself.