Devious; cunning — using sly or underhanded methods to gain advantage; crafty and calculating.
彼はずる賢い手口で契約を有利に進めた。
He advanced the contract to his advantage using cunning tactics.
子どもにずる賢い行動を教えるのは避けたい。
I want to avoid teaching children to behave slyly.
最初はずる賢いと思っていたが、事情を聞いて考えが変わった。
At first I thought he was crafty, but after hearing the circumstances my view changed.