xiāo rǎng zhī bié
see 天壤之別|天壤之别[tian1 rang3 zhi1 bie2]
霄
xiāo
firmament
壤
rǎng
(bound form) soil; earth
之
zhī
(possessive particle, literary equivalent of 的[de5])
别
bié
to leave; to part (from)