I have always pondered why they classify zoas as easy to keep as certain strains just have dismal track records in captivity (Notably African species). If anything is off in my tank my zoas are usually the first to show signs of stress, at times I think SPS is easier to keep
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I have a feeling the reason that zoas are classified as a beginner coral is because of the lower light and feeding requirements that go along with them. That being stated the diversity of the genus/ species is so vast we run into problems classifying them as the same coral and caring for them accordingly. Some polyps seem to be much more resilient to water fluctuations while others melt very easy, unlike SPS or LPS the lack of a predominant calcareous skeleton means these corals are more susceptible to predation also.
Out of all of my corals zoas are the most sensitive to ALK swings, temp fluctuations and irritation from pests (Such as Pods, worms or fish).
Levi