朝秦暮楚

zhāo qín mù chǔ

serve Qin in the morning Chu in the evening (idiom); quick to switch sides

zhāo

morning

qín

short name for 陝西|陕西[Shan3 xi1]

evening

chǔ

abbr. for Hubei 湖北省[Hu2 bei3 Sheng3] and Hunan 湖南省[Hu2 nan2 Sheng3] provinces together