剁成幾斷 Chopped Into Several Pieces
那駙馬聞言，即使月牙鏟，帶龍孫往外殺來。這八戒舉鈀迎敵，且戰且退，跳出水中。這岸上齊天大聖與七兄弟一擁上前，槍刀亂扎，把個龍孫剁成幾斷肉餅。那驸马闻言，即使月牙铲，带龙孙往外杀来。这八戒举钯迎敌，且战且退，跳出水中。这岸上齐天大圣与七兄弟一拥上前，枪刀乱扎，把个龙孙剁成几断肉饼。
逐句解 Line by line
The son-in-law, hearing it, took up his crescent-moon spade and came fighting out with the dragon grandsons.
那 is deictic. 即使 here is not the concessive even-if but two separate graphs — at once, and to use — and the spade is the same weapon named in the first description of him.
Eight Rules raised his rake to meet them, fighting and giving ground by turns, and leapt out of the water.
鈀 is pá and 中 is zhōng. 且戰且退 — fighting and retreating at once — is the manoeuvre, and it is the manoeuvre he was told to perform: the whole of his part is to lose ground in a useful direction.
On the bank the Great Sage Equal to Heaven and the seven brothers rushed forward together, spears and blades stabbing every way, and chopped a dragon grandson into so many lumps of minced meat.
扎 keeps zhā, the free verb to stab. The corpus reads the same graph zhá inside the fixed binome 掙扎, and the split is of a kind this chapter has met twice already — a set compound keeping its conventional reading while the free morpheme takes its own. 一擁 takes 一 at yì. No graph here stands in any guard roster.
The ambush works exactly as designed, and the design is not flattering to anybody. Eight Rules goes in, kills a mourner, is chased out, gives ground on purpose, and eight armed immortals fall on whatever follows him. The dragon grandson who comes out first is dead before the passage ends.
剁成幾斷肉餅 is the most physical thing in the chapter. 肉餅 is minced meat pressed into cakes — a kitchen word — and putting it at the end of a line about spears and blades makes the killing domestic rather than martial.
The arithmetic is worth stating. 七兄弟 here counts Erlang together with his six, so eight are waiting on the bank with Pilgrim among them, while one pig does the work in the water. Against the eight, the household has a son-in-law and whatever grandsons are left.