孜孜矻矻

zī zī kū kū

diligently

孜

zī

used in 孜孜[zi1 zi1]

孜

zī

used in 孜孜[zi1 zi1]

矻

kū

used in 矻矻[ku1 ku1]

矻

kū

used in 矻矻[ku1 ku1]