I've done ZEN on zhash.pro (good experience), ZEC on flypool (minimal rejects and good experience), ZEC on dwarfpool (massive rejects), and am right now doing ZEN on luckpool with a 52-54 kSol average and 0% rejects. I've played with mining a single coin at a single pool, and also using Awesome Miner to profit switch between dwarfpool and luckpool.

My struggle so far with profit switching is a) finding good pools that have solid hash power going and that have proportional payouts, and b) losing a bit of time while the miner ramps up after a switch. The more you switch, the more time you lose. The less you switch, the less benefit you get from the profit switching method. Additionally, dealing with three different coins complicates my own calculations of daily efficiency and profitability versus just one and done.

I'm always happy to try out possible better options - what is the URL and port you're using for an ASIC on nanopool?