Enlightenment is Not What You Think
Zen is directly experienced "sudden awakening" -- or Enlightenment. (Satori)
Zen is also "seeing directly into your original nature in a flash and becoming a buddha (awakened one)" (Kensho)
Suddenly awakened to what? "Seeing directly" into what? Since objects and subject both get dropped completely in satori, the question is unanswerable.
You will know it when and if it happens, but the "you" that knows won't be who you "think."
There are many "records" of the sayings and doings of Zen Masters. Every single one of these Masters at some point in life got suddenly enlightened (awakened).
Some got awakened while sitting in Zen meditation. Others, while raking a courtyard, or rolling up a bamboo screen, or begging for a bowl of rice, or having a foot broken in a slammed monastery gate.
"Ahgg! But it's so frustrating! What do you mean by 'awakened'? Why can't you define it? How do I get there?"
You can't get there, because when it happens you won't be there. Or, at least, the "thinking" you that you mistake yourself for won't be, while the you you really and brilliantly are -- and have been since before the birth of this or any other universe -- will!