Xiao Ke will answer, but I don’t have much research on calligraphy, but I know a little bit about ancient Chinese.
This couplet should mean that Zhang Xu’s calligraphy has been mastered. In the realm of gods, when the pen falls on the paper, it is like entering the clouds and misty mist. It is the eighth artistic conception of ancient and modern calligraphy. (It can also be translated as this kind of calligraphy. There are eight ways of writing, but it may be too small.) Drink until you are happy. At that time (that is, what northerners call drunkenness), the house is full of turmoil (that is, the scene is lively and spectacular, by association) at the end of the year, three glasses of wine should be commemorated.
This is to describe Zhang Xu’s calligraphy as if he was in a no-man’s land after drinking like a drunken boxer