First attested in 810 CE, in Han Yu's prose:

與之語道理，辨古今事當否，論人高下，事後當成敗，若河決下流而東注，若駟馬駕輕車就熟路，而王良、造父為之先後也，若燭照數計而龜卜也。

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与之语道理，辨古今事当否，论人高下，事后当成败，若河决下流而东注，若驷马驾轻车就熟路，而王良、造父为之先后也，若烛照数计而龟卜也。

From: 810, 韓愈,《送石處士序》

Yǔ zhī yǔ dàolǐ, biàn gǔjīn shì dàng fǒu, lùn rén gāoxià, shìhòu dàng chéngbài, ruò hé jué xià liú ér dōng zhù, ruò sìmǎ jià qīng chē jiù shú lù, ér Wáng Liáng, Zàofǔ wèi zhī xiānhòu yě, ruò zhú zhào shù jì ér guī bǔ yě.

When he reasons with others his eloquence is like the River overflowing and running eastward; when he discusses the right and wrong of ancient and contemporary affairs he is so sure of his ground that it is like a four-horse carriage driven through familiar roads with Wang Liang and Tsao Fu taking the reins; and when he assesses the abilities of men and their future success or failure, his prognostication is as clear and revealing as examining under candlelight, counting by numbers or divining with the aid of tortoise shells.

駕輕就熟

1. to perform a task with which one is very familiar with great ease; (to deem a task) a piece of cake; (to go for) a hay ride

• 輕車熟路／轻车熟路 (qīngchēshúlù)