zī zī bù juàn
lit. diligent and never slacking (idiom); continuous concentrated effort
assiduous (in study)
to concentrate
bù juàn
tireless
untiring
indefatigable
huì rén bù juàn
instructing with tireless zeal (idiom, from Analects)
xué ér bù yàn , huì rén bù juàn
study tirelessly, teach with endless enthusiasm (idiom, from Analects)