break apart vs split up

break apart is not a noun while split up is a noun.

Word	Noun	Adjective	Verb	Adverb
break apart	No	No	Yes	No
split up	Yes	No	Yes	No

As verbs, split up is a hypernym of break apart; that is, split up is a word with a broader meaning than break apart:

Other hypernyms of break apart include break, break up, part, separate, split.

break apart (noun)	split up (noun)
	an increase in the number of outstanding shares of a corporation without changing the shareholders' equity

break apart (verb)	split up (verb)
break up or separate	become separated into pieces or fragments
break violently or noisily; smash	get a divorce; formally terminate a marriage
take apart into its constituent pieces	discontinue an association or relation; go different ways
	separate into parts or portions