连 … 都 … ，何况 … (even …, let alone …)

Even adults struggle

• Your little cousin wants to read a university textbook.
• this这zhè本书běn shūeven连liánadult大人dà rén(even)都dōuunable to make sense of…看不懂kàn bù dǒng，let alone何况hé kuàngchild小孩子xiǎo hái zi(and …? / softener)呢ne？ — "Even adults can't understand this book, let alone a small child."

even连lián A (even)都dōu …，let alone何况hé kuàng B ((and …? / softener)呢ne)？

• even连lián A (even)都dōu …，let alone何况hé kuàng B = even A …, let alone B: if it holds (or fails) for A, it is even more so for B.
• let alone何况hé kuàng often ends with (and …? / softener)呢ne as a rhetorical question.

even连liánexperts专家zhuān jiā(even)都dōudon't不bùknow知道zhī dào，let alone何况hé kuàngus我们wǒ men呢ne？

Positive too

• he他tāeven连liánthe hardest最难zuì nánones的dequestions题tí(even)都dōucan会huìdo做zuò，let alone何况hé kuàngsuch这么zhè meeasy简单jiǎn dānones的de？ — "He can do even the hardest questions, let alone such an easy one."
• The logic runs from the harder case to the easier one.

he他tāeven连liánthe hardest最难zuì nán的dequestions题tí(even)都dōucan会huìdo做zuò，let alone何况hé kuàngsuch这么zhè meeasy简单jiǎn dānones的de？

Get the direction right

let alone何况hé kuàng versus more更gèngneedless to say不用说bú yòng shuō

• more更gèngneedless to say不用说bú yòng shuō…(completed / change)了le is a statement: adult大人dà rén(even)都dōuunable to make sense of…看不懂kàn bù dǒng，more更gèngneedless to say不用说bú yòng shuōchild孩子hái zi(completed / change)了le.
• let alone何况hé kuàng…(and …? / softener)呢ne？ is often a rhetorical question and a little more literary.

too太tàifar远yuǎn了le，besides何况hé kuàngit天tiānalso也yělate晚wǎn了le。

Recap

Read the full reference: HSK 6 grammar — Let alone.