？
It's not good to nitpick at other people's work, you know?
Literal
People [genitive-の] work [to-に] put-fault [nominalizer-の] [topic-は] not-good [assertive-ぞ]?
Mild workplace reproach. けちをつける is a set expression literally 'attach a stinginess,' meaning 'to nitpick,' 'to find fault with,' 'to criticize pettily.' 人の仕事にけちをつける = 'find fault with someone's work.' 仕事にけちをつける = 'nitpick at someone's job/output.' The に marks the target of the criticism. The sentence-final ぞ is a masculine assertive particle, firmer than よ, used to emphasize a point with authority or caution. The question mark after suggests the speaker is making the criticism as a near-rhetorical challenge ('it's not good, you know?').