In fact, in the history of calligraphy, running scripts are ranked, such as Wang Xizhi's Preface to Lanting Collection, Yan Zhenqing's Sacrifice to My Nephew, and Su Dongpo's Huangzhou Cold Food Poetry. Later people ranked down on the basis of three running scripts, and some even ranked the top ten running scripts in the world.
But for regular script, there is no ranking in history. Only Zhong You is recognized as the originator of regular script, and there are many regular script masters. Wang Xizhi, Wang Xizhi and Zhong You were all regular script masters, and later Ou Yangxun, Liu Gongquan and Yu Shinan were all regular script masters. But why can Yan Zhenqing become the "first regular script"?
I think this has something to do with Yan Zhenqing's great innovation in style. First of all, Yan Zhenqing innovated brushwork, integrated the brushwork of seal script into regular script, combined with the bold brushwork of inscriptions in the Northern and Southern Dynasties, and wrote a style completely different from Wang Xizhi's calligraphy style. The brushwork changed from the inside out, and the calligraphy style was calm, which found its own direction for the writing of regular script.
On the other hand, Yan Zhenqing's calligraphy works are too numerous and varied. Each copybook has its own unique features, such as many pagodas, strict elegant tablets, powerful temple tablets, fairy tales of Magu, etc., which are only different from those of calligraphers such as Liu Gongquan in one or two ways. Only a real master can do this.
Yan Zhenqing is known as "the first regular script" for his innovative brushwork and diverse styles.