君の計画は砂上の楼閣に過ぎないよ。

tbd

Your scheme is like a house built on the sand.

基礎に杭を打ち込むのを忘れて、空中に楼閣を建てるとは、あなたも愚かな人だ。

tbd

It is foolish of you to build a castle in the air while forgetting to drive in pilings for its foundation.