split up vs fragmentize

split up is a noun but fragmentize is not a noun.

Word	Noun	Adjective	Verb	Adverb
split up	Yes	No	Yes	No
fragmentize	No	No	Yes	No

As verbs, fragmentize is a hyponym of split up; that is, fragmentize is a word with a more specific, narrower meaning than split up:

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

split up (verb)	fragmentize (verb)
become separated into pieces or fragments	break or cause to break into pieces
get a divorce; formally terminate a marriage
discontinue an association or relation; go different ways
separate into parts or portions