2 old iron cow
The four masters of regular script are the collective names of four calligraphers who are famous for regular script in the history of calligraphy. Regular script, also known as Four Books, has four styles in Yuan Dynasty: European style, Yan Zhenqing style, Liu Gongquan style and Zhao Mengfu style.
4 Huai bing
Fifty thousand Qi Wang Xin.
The first pain is a verb, and ... it is a kind of pain.
The second bitterness is a noun, something bitter.
The third bitterness is also a noun, a bitter thing.
The whole sentence means that if suffering is bitter, then suffering is endless.