Original sentence: The Exodus of Kashmiri Hindus, who are also called "Kashmiri Pandits", is the migration, especially en mass, or the  flight, especially large-scale, of Hindus that caused their displacement from the Kashmir Valley,
Edited sentence: The Exodus of Kashmiri Hindus, who are also called "Kashmiri Pandits", is the migration, especially en mass, and also the  flight, especially large-scale, causing displacement of Hindus from of the Kashmir Valley,