Complex sentence: The major groups of this classification, Mandarin, Wu, Yue, Southern Min and so on, are not mutually intelligible, though many varieties within each of these groups are also mutually unintelligible.
Split into simpler sentences: The major groups of this classification, Mandarin, Wu, Yue, Southern Min and so on, are not mutually intelligible. In fact, many varieties within each of these groups are also mutually unintelligible.