～はもとより— Let Alone (Formal)

• この製品は国内はもとより、海外でも人気だ。

  Kono seihin wa kokunai wa motoyori, kaigai de mo ninki da.

  This product is popular abroad, not to mention domestically.

  国内はもとより treats the domestic market as a given, adding overseas

• 彼は漢字はもとより、ひらがなも書けなかった。

  Kare wa kanji wa motoyori, hiragana mo kakenakatta.

  He couldn't write hiragana, let alone kanji.

  はもとより sets kanji as the obvious case, adding the more basic hiragana

• 社長はもとより、社員全員がその計画に賛成した。

  Shachou wa motoyori, shain zen'in ga sono keikaku ni sansei shita.

  Not to mention the president, all the employees agreed to the plan.

  はもとより frames the president as expected and adds all staff

• ・Register: formal/written; less common in casual conversation.
• ・Interchangeable in meaning with はもちろん, but more elevated in tone.
• ・The second item usually takes も.

Commonly confused with

The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones ～はもとより is tested against.

• ～上は — Now That the Die Is Cast
• ～ことなく — Without Ever
• ～ことになっている — It's The Rule
• ～つつある — In the Process of Changing
• ～において／～における — In; At; Regarding (Formal)
• ～に関して／～に関する — Regarding; Concerning
• ～にしろ／～にせよ — Whether One Way or Another
• ～に沿って — Following the Line