Complex sentence: A special characteristic of zǐshā clay is that it holds heat for a long time; this has the unfortunate side effect of making it easy to overcook delicate green teas, which typically need lower temperature water.
Split into simpler sentences: A special characteristic of zǐshā clay is that it holds heat for a long time. This make it easy to overcook delicate green teas during their preparation, which typically need lower temperature water.