彼の説明はちんぷんかんぷんで、何を言っているのかさっぱりわからなかった。
His explanation was complete gibberish; I had no idea what he was talking about.
There's too much jargon; it's all Greek to me.
His explanation was complete gibberish to me.
There were so many technical terms that the conversation became incomprehensible.
This math problem is total gibberish to me.
ちんぷんかんぷん is a casual expression for something totally incomprehensible, while 禅問答 keeps a Zen-riddle flavor even when used figuratively for baffling talk.
Ateji kanji form; rarely used.
Ateji kanji form; rarely used.