let alone

～はもちろん、～は言うまでもなく、まして～なんて
※否定+否定で使う

Ex

• He cant’t speak French, let alone German.
• I don’t have a cent, let alone a dollar.

Reference source

• https://eow.alc.co.jp/search?q=let%20alone
• https://reibunpo.com/let/let-alone.shtml