Yan Gu: It means that both kinds of calligraphy are very powerful, but their styles are different. Also known as excellent calligraphy. Yan: Yan Zhenqing, a calligrapher in the Tang Dynasty; Liu: Liu Gongquan, a calligrapher in the Tang Dynasty.
Flowing clouds and flowing water: It is a metaphor for the layout and development of articles, which is as natural as the movement of clouds and the flow of water without carving. Su Shichuan, History of the Song Dynasty: "Writing is like running water, which has no definite quality at first, but ends up in its proper place.".