"was a man whom God took into paradise and who heard things" or "was a man whom an angel took into paradise and who heard inexpressible words."or "was a man who entered into paradise and heard inexpressible words" or "was a man who suddenly appeared in paradise and heard inexpressible words."
Possible meanings of "inexpressible" are that 1) Paul means something other than "it is unlawful for people to speak" these words, and so people are unable to communicate the ideas expressed in the words or 2) Paul means the same thing as "it is unlawful for people to speak" these words, emphasizing that God does not permit people to speak the words.