Complex sentence: The Ismā'īlī lay special emphasis on purity and it's related practices, and the Nizari consider this in a more esoteric sense too and apply it to purity of mind, soul and action, the Musta'lis also apply it to ritual practices related to prayer and cleanliness.
Split into simpler sentences: The Ismā'īlī lay special emphasis on purity and it's related practices. While the Nizari consider this in a more esoteric sense and apply it to purity of mind, soul and action, the Musta'lis also apply it to ritual practices related to prayer and cleanliness.