lip-sync vs lip-synch

lip-sync and lip-synch both are verbs.

Word	Noun	Adjective	Verb	Adverb
lip-sync	No	No	Yes	No
lip-synch	No	No	Yes	No

As verbs, lip-sync and lip-synch are synonyms defined as:

lip-sync and lip-synch: move the lips in synchronization (with recorded speech or song)

lip-sync (verb)	lip-synch (verb)
move the lips in synchronization (with recorded speech or song)	move the lips in synchronization (with recorded speech or song)