Literally, 'work of Chinese people'; a colloquial expression for work that is extremely tedious, painstaking, delicate, or requires great patience and attention to minute detail; considered offensive because it stereotypes an ethnic group.
2.
SpainLatin Americacolloquialinformalderogatory
Figuratively, a task that is needlessly complicated or that becomes ruined by a small mistake despite much effort.
Examples:
ES: ¡Es un trabajo de chinos!
EN: That's an herculean task!
ES: Los yanquis habrían presionado para paralizar el proyecto. Un trabajo de chinos a la mierda por un estúpido error.
EN: The Yanks would have brought all our hard work to a halt.