If you were using Ethos previously to mine ETH and you have switched to ZEC, make sure you reset any overclocks you were using in ETH mining back to factory settings. ZEC doesn't respond very well to any overclocks (including those done via BIOS mods).
When I first switched over I had left all the overclocks and it made my rigs very unstable. Since I reset everything back my rigs are fine. I've run them without reboot for at least 12 hours each.
The exception is a single Sapphire R9 390 nitro card, which will mine for up to 1 hour, then it reports temperature of 128 degrees, or 0 degrees, then it stops - so I removed this card and then it's all fine. This 390 is perfectly fine when mining ETH, for days - overclocked, but not mining ZEC. I don't know if that helps, but it's my experience with EthOS ZEC so far.
Initially flypool was terrible so I switched to nanopool and it's been great.