bend vs zig-zag fold

bend and zig-zag fold both are nouns.

Word	Noun	Adjective	Verb	Adverb
bend	Yes	No	Yes	No
zig-zag fold	Yes	No	No	No

As nouns, zig-zag fold is a hyponym of bend; that is, zig-zag fold is a word with a more specific, narrower meaning than bend:

bend: an angular or rounded shape made by folding
zig-zag fold: a continuous parallel folding in an accordion-like fashion, that is with folds alternatively made to the front and back in zig-zag folds.

Other hyponyms of bend include plait, pleat, kink, twirl, twist, pucker, ruck, accordion fold, concertina fold, z-fold.

bend (noun)	zig-zag fold (noun)
curved segment (of a road or river or railroad track etc.)	a continuous parallel folding in an accordion-like fashion, that is with folds alternatively made to the front and back in zig-zag folds.
diagonal line traversing a shield from the upper right corner to the lower left
movement that causes the formation of a curve
an angular or rounded shape made by folding
a circular segment of a curve

bend (verb)	zig-zag fold (verb)
cause (an object) to assume a crooked or angular form
bend a joint
form a curve
change direction
turn from a straight course, fixed direction, or line of interest
bend one's back forward from the waist on down