expression, i-adjective
unmotivated; lacking drive; unenthusiastic
Describes a person who lacks the energy or will to do something, often used in casual or dialectal speech. The word ずく itself is a dialectal or colloquial term for motivation or initiative.
最近ずくがなくて、何もする気になれない。
Lately I've been unmotivated and can't bring myself to do anything.
彼はずくがないから、誘っても来ないよ。
He's so unenthusiastic that even if you invite him, he won't come.