endeavor vs undertaking

endeavor and undertaking both are nouns.

Word	Noun	Adjective	Verb	Adverb
endeavor	Yes	No	Yes	No
undertaking	Yes	No	No	No

As nouns, undertaking is a hypernym of endeavor; that is, undertaking is a word with a broader meaning than endeavor:

endeavor: a purposeful or industrious undertaking (especially one that requires effort or boldness)
undertaking: any piece of work that is undertaken or attempted

Other hypernyms of endeavor include labor, labour, project, task.

endeavor (noun)	undertaking (noun)
earnest and conscientious activity intended to do or accomplish something	any piece of work that is undertaken or attempted
a purposeful or industrious undertaking (especially one that requires effort or boldness)	the trade of a funeral director

endeavor (verb)	undertaking (verb)
attempt by employing effort