spice vs zest

spice and zest both are nouns.

Word	Noun	Adjective	Verb	Adverb
spice	Yes	No	Yes	No
zest	Yes	No	Yes	No

As nouns, zest is a hyponym of spice; that is, zest is a word with a more specific, narrower meaning than spice:

As verbs, spice and zest are synonyms defined as:

Other synonyms of spice include spice up.

spice (noun)	zest (noun)
the property of being seasoned with spice and so highly flavored	a tart spicy quality
any of a variety of pungent aromatic vegetable substances used for flavoring food	vigorous and enthusiastic enjoyment
aromatic substances of vegetable origin used as a preservative

spice (verb)	zest (verb)
make more interesting or flavorful	add herbs or spices to
add herbs or spices to