Gǎigé shì yí gè chángqī guòchéng, bùnéng yīcù'érjiù.
Reform is a long-term process that cannot be achieved in one stroke.
Tips
history
From Su Xun's Song-era 《上田枢密书》: 「天下之学者,孰不欲一蹴而造圣人之域」 — 'what scholar does not wish to reach the sage's realm in a single step?' Su Xun was criticizing impatience, which is how the phrase is still used.
usage
Almost always appears in a negative construction: 不能一蹴而就 / 不是一蹴而就的 ('cannot be / isn't a one-stroke matter'). The phrase exists mainly to deny that something can be rushed.