yíng rèn ér jiě
lit. (bamboo) splits when it meets the knife's edge (idiom)
fig. easily solved
dāo rèn
knife blade
crucial point
yóu rèn yǒu yú
handling a butcher's cleaver with ease (idiom); to do sth skillfully and easily
bīng bù xuè rèn
lit. no blood on the men's swords (idiom); fig. an effortless victory
shuāng rèn jiàn
double-edged sword (both lit. and fig.)