Purple Tongzhi Sword began in the Warring States Period, and reigned in the Zhou Dynasty, ending in the last week of the Five Dynasties. Zi Jian, Zhang's annotation, began in Song and Yuan Dynasties. Based on Zi Jian, Zhang took its important paragraphs and extracted the biography of Song Tongjian and Ming Song and Yuan Tongjian.
It's easier to understand, and after adding comments, I feel more deeply understood. This set of books is really good.