三山之功 The Feat of the Three Mountains
二魔笑道：「哥啊，你也忒會擡舉人。若依你誇獎他，天上少有，地下全無；自我觀之，也只如此，沒甚手段。」老魔道：「你拿住了？」二魔道：「他已被我遣三座大山壓在山下，寸步不能舉移。所以才把唐僧、沙和尚連馬、行李，都攝將來也。」二魔笑道：「哥啊，你也忒会抬举人。若依你夸奖他，天上少有，地下全无；自我观之，也只如此，没甚手段。」老魔道：「你拿住了？」二魔道：「他已被我遣三座大山压在山下，寸步不能举移。所以才把唐僧、沙和尚连马、行李，都摄将来也。」
逐句解 Line by line
The second fiend laughed: "Brother, you do overpraise the fellow.
忒會擡舉人 (tè huì tái jǔ rén) is "far too good at building people up," 擡舉 being the act of raising someone in others' estimation. The younger brother thinks his elder is star-struck.
"To hear you praise him, he'd be rare in heaven and unmatched on earth — but as I see it, he's nothing so much, no great skill to him."
And here is the sneer the chapter has been setting up. 天上少有，地下全無, "seldom in heaven and nowhere on earth," is the second demon mocking a formula the reader last heard twenty-three passages ago in the master's astonished praise, 寰中少有，世上全無. Same shape, same joke, opposite intent. 自我觀之 (zì wǒ guān zhī), "as I see it," 觀 read guān; 沒甚手段, "nothing much to him," with the question-word shén.
The old fiend said: "Have you caught him, then?"
拿住了 (ná zhù le), "and did you actually catch him?" One flat question, and it deflates the boast without raising a voice.
The second fiend said: "I've already sent three great mountains to press him down beneath them — he can't stir so much as an inch.
遣三座大山 (qiǎn sān zuò dà shān), "sent three great mountains" -- Sumeru, Emei and Tai, in that order. 寸步不能舉移 (cùn bù bù néng jǔ yí) is a set phrase, "unable to shift by so much as a step"; the 寸 in it works like the "inch" of "he never budged an inch," a figure of speech rather than anything measured. When the chapter does measure something in 寸 later on, it means it literally.
"That's why I was able to fetch Tripitaka, Sha Monk, the horse, and the baggage, and carry them all here."
連馬、行李 (lián mǎ, xíng lǐ), "horse and baggage and all." 攝將來 (shè jiāng lái), "spirited them over here," 將 the syllable of motion again. And there is his answer to his brother's complaint buried in the boast: the master could only be taken because the guardian was buried first.
The younger fiend meets caution with a boast, dismissing the Monkey King as nothing much. The irony is thick, because the reader has just watched Pilgrim shrug two mountains onto his shoulders and run under them faster than a horse, and knows the elder brother's estimate is the accurate one. Contempt of this kind is how such villains are usually undone.
And yet the boast contains its own answer to the worry. He pinned Pilgrim under three mountains, and that is exactly why the rest could be taken. The exchange settles the brothers' quarrel and, in the same breath, plants the fault line the story will open: a Great Sage who has been pinned rather than killed is a Great Sage who may work loose.