How did parallel prose develop in the Tang Dynasty?

Parallel prose in the Tang Dynasty, as an applied style of official imperial edict, has always been a compulsory subject for scholars. "Han (Yu) and Li (Ao) are determined to go back to the ancients, but they cannot change the trend of parallel prose in the world" (Zeng Guofan's Preface to Hunan Literary Prose). Compared with the Six Dynasties, parallel prose in the Tang Dynasty changed. First, it was pragmatic and practical, which changed the disadvantages of parallel prose in the Six Dynasties, such as Wei Zhi, Lu Zhi and others mocking Chen Shizhi's illness. First, in terms of antithesis, melody and rhetoric, Shang Hua's literary talent is brilliant, but he has his own characteristics in understanding Xiao Chang (Lu Zhi), gorgeous rhetoric (four outstanding figures) and exquisiteness and elegance (Li Shangyin). The general development trend of parallel prose in Tang dynasty is scattered, which is caused by absorbing some advantages of ancient prose.