才好幹事 Only Then Can He Work
我老豬本來有三十六般變化，若說變輕巧華麗飛騰之物，委實不能；若說變山，變樹，變石塊，變土墩，變賴象、科豬、水牛、駱駝，真個全會。只是身體變得大，肚腸越發大。須是吃得飽了，才好幹事。」我老猪本来有三十六般变化，若说变轻巧华丽飞腾之物，委实不能；若说变山，变树，变石块，变土墩，变赖象、科猪、水牛、骆驼，真个全会。只是身体变得大，肚肠越发大。须是吃得饱了，才好干事。」
逐句解 Line by line
"Old Pig has thirty-six transformations by nature. If you talk of turning into things light and elegant and able to fly, then truly I cannot; but if you talk of turning into a hill, a tree, a lump of rock, a mound of earth, a mangy elephant, a boar, a water buffalo or a camel, then I can do the whole of it.
Two halves of one sentence cut by a semicolon and rejoined: 若說變X，委實不能 against 若說變Y，真個全會 — the same frame at the same depth, a denial and then an affirmation. 華 is huá in 華麗, splendid, where the same character read huà in the mountain's name earlier in this chapter.
"Only, when the body is changed large, the belly and bowels grow larger still.
The catch, and it is a matter of plumbing. 得 is the full verb dé here, carrying its own complement: the body changes large, and the gut changes larger. Scale up a pig and you scale up its appetite faster.
"So I must eat my fill first; only then can I do the work."
好 is hǎo here, modifying the verb after it — the ordinary reading, not the hào of being fond of something that the same character took when he was talking about beating dead snakes.
The catalogue of transformations is the fifth list Eight Rules has produced in this chapter and the only one about himself. It is organised as a denial and then an affirmation, and the denial comes first: nothing light, nothing elegant, nothing that flies.
What he can do is heavy and all of it belongs to the ground: hill, tree, rock, earth, and then four large animals finishing with a camel. The list defines him by sheer mass, which happens to be exactly the qualification the job calls for.
The condition attached is the point of the scene. A larger body means a larger gut, so the transformation comes with a running cost, and the village is about to be asked to meet it.