Complex sentence: It goes on to describe how Jiang Biwei was having an affair herself with the married official Zhang Daofan and that it was Zhang who suggested Xu had been having an improper relationship in order to further drive a wedge between the couple.
Split into simpler sentences: It goes on to describe how Jiang Biwei was having an affair herself with the married official Zhang Daofan. It was Zhang who suggested Xu had been having an improper relationship in order to further drive a wedge between the couple.