epic vs heroic verse

epic and heroic verse both are nouns.

Word	Noun	Adjective	Verb	Adverb
epic	Yes	Yes	No	No
heroic verse	Yes	No	No	No

As nouns, heroic verse is a hyponym of epic; that is, heroic verse is a word with a more specific, narrower meaning than epic:

epic: a long narrative poem telling of a hero's deeds
heroic verse: a verse form suited to the treatment of heroic or elevated themes; dactylic hexameter or iambic pentameter

Other hyponyms of epic include chanson de geste, rhapsody, heroic, heroic meter.

epic (noun)	heroic verse (noun)
a long narrative poem telling of a hero's deeds	a verse form suited to the treatment of heroic or elevated themes; dactylic hexameter or iambic pentameter

epic (adjective)	heroic verse (adjective)
constituting or having to do with or suggestive of a literary epic
very imposing or impressive; surpassing the ordinary (especially in size or scale)