The Shangyuan Ancient Scripture practiced by Yang Zhen was just a spiritual level cultivation method, and it was only because of a lucky coincidence that Yang Zhen managed to enhance the quality of the Shangyuan Scripture.
However, the highest quality Shangyuan Ancient Scripture was also just a spiritual level cultivation method. Yang Zhen had once tried to comprehend it, wanting to upgrade its quality, but it came to no fruition in the end.
It wasn't that Yang Zhen lacked talent, but the limitations of the Shangyuan Ancient Scripture restricted the realization of Yang Zhen's talent.