It's beyond me. 侧重于说情感上的无法理解；It's all Greek to me. 侧重于说对技术等一窍不通
示例
A：Do you know why Tom quit such a high paying job?
B：It's beyond me.
A：你知道为什么汤姆要辞掉这个高薪的工作啊？
B：我不知道。
A：Didn't he tell you how to use it?
B：What he said is too professional. It's all Greek to me.
A：他没有告诉你怎么用吗？
B：他说得太专业了，我听不懂。