challenging vs thought-provoking

challenging and thought-provoking both are adjectives.

Word	Noun	Adjective	Verb	Adverb
challenging	No	Yes	No	No
thought-provoking	No	Yes	No	No

As adjectives, challenging and thought-provoking are synonyms defined as:

challenging (adjective)	thought-provoking (adjective)
requiring full use of your abilities or resources	stimulating interest or thought
disturbingly provocative
stimulating interest or thought