let alone; needless to say ~
This pattern means 'let alone' or 'needless to say', emphasizing that something is true of a basic or minimal item, so it is certainly true of a more extreme or obvious one.
はおろか is a formal, written pattern used to say 'not to mention' or 'let alone'. It presents a stronger statement after the phrase, and the clause before it is something that might be considered minimal or basic. For example, if you say '子供はおろか、大人もできない' it means 'Not to mention children, even adults can't do it.' The pattern often carries a tone of surprise or emphasis that even the basic case is true or not true, so of course the extreme case follows.