According to the plot, the original author of Princess Taiping should be Wu Zetian, because in order to please Li Shimin, Wu Zetian made great efforts in literary attainments, and had to admit that she had made small achievements in calligraphy and poetry, and even Li Shimin was promoted. It's a pity that her personality is too cruel and violent, and she is not Li Shimin's favorite object, so she is left out in the cold, while Li Shimin himself just likes calligraphy very much and collects it. According to unofficial history's official records, the original of the famous Preface to the Lanting Pavilion was buried with him. Therefore, it is recorded in Records of the Historian Calligraphy that Wu Zetian: Wu Zetian 13 and 14 were well-read at the age of four, and were good at poetry and lyrics, with exquisite calligraphy and elegant fonts. Therefore, Princess Taiping worshipped her mother very much and her personality was like Wu Zetian, so she was deeply loved by Wu Zetian.
If you're asking body double, generally speaking, the people who appear in this kind of drama are the book association or ghostwriters. As for who he is, no one knows, only ask the crew!