天理難容 Heaven Will Not Allow It
這一去，那國王不戰則可，戰必不利。我大王使煙火飛沙，那國王君臣百姓等，莫想一個得活。那時我等占了他的城池，大王稱帝，我等稱臣。雖然也有個大小官爵，只是天理難容也。」这一去，那国王不战则可，战必不利。我大王使烟火飞沙，那国王君臣百姓等，莫想一个得活。那时我等占了他的城池，大王称帝，我等称臣。虽然也有个大小官爵，只是天理难容也。」
逐句解 Line by line
"On this errand, if that king will not fight, well and good; but if he fights it must go badly for him."
則可 is a literary formula marking the acceptable branch of an either-or, and it sounds oddly stiff in a mouth that has just said some-such-war-letter twice. He slips into the register of the documents he is carrying the moment he starts predicting.
"When our Great King looses his smoke and fire and flying sand, that king and his ministers and his commons — not one of them may hope to come out alive."
得 is dé, to manage to, following 莫想 — do not imagine you will. The three weapons get named in one breath by somebody who has never had to stand in them, and in a third order again: the chapter's title has them smoke, sand, fire; the narrative delivered them fire, smoke, sand; and he says smoke, fire, sand.
"Then we shall have taken his walls and moats, and the Great King will style himself emperor and we shall style ourselves his ministers."
稱 twice in eight characters, once for the master and once for the followers, and the same verb does for both — to style oneself, which is a claim rather than an appointment. 城池 is walls-and-moat together, the standing pair for a city considered as a thing that can be taken.
"There will be ranks and offices for us, high and low, no doubt — only Heaven's own principle will never allow it."
難 is nán, hard to, not the nàn of disaster: 天理難容 says Heaven can hardly find room for such a thing. Everything before the 只是 is his own side's case, laid out fairly, and then he refuses it.
He lays out the campaign competently and correctly — smoke, fire, sand, a certain massacre, the walls taken, the titles handed round — and then ends on a sentence that undoes the lot. He is not persuaded by his own side. He has worked out what the promotion is worth and concluded that Heaven will not stand for what earns it.
He has already passed judgement on his master once in this speech, calling him cruel-hearted at its opening; this is the same verdict again with Heaven behind it, delivered to nobody on an empty road. Wukong is sitting on the despatch bag listening, so the one audience for the verdict is the person already committed to enforcing it.
The prediction is right in every particular except its conclusion. The smoke and fire and sand are real and would do exactly what he says; the walls could be taken. What he has wrong is only that the match for his master — the one he has just dismissed as some Sun Pilgrim or other — is riding on his back.