piece of cake vs project

piece of cake and project both are nouns.

Word	Noun	Adjective	Verb	Adverb
piece of cake	Yes	No	No	No
project	Yes	No	Yes	No

As nouns, project is a hypernym of piece of cake; that is, project is a word with a broader meaning than piece of cake:

Other hypernyms of piece of cake include labor, labour, task, undertaking.

piece of cake (noun)	project (noun)
any undertaking that is easy to do	any piece of work that is undertaken or attempted
	a planned undertaking

piece of cake (verb)	project (verb)
	present for consideration, examination, criticism, etc.
	regard as objective
	communicate vividly
	throw, send, or cast forward
	transfer (ideas or principles) from one domain into another
	imagine; conceive of; see in one's mind
	make or work out a plan for; devise
	put or send forth
	draw a projection of
	cause to be heard
	project on a screen
	extend out or project in space