There's a second make-up artist associated with the film, former silent-era actor Carl Axzelle (whose thick Swedish accent caused him to retreat behind the camera when talkies came in).

My money would be on Axzelle having been in charge of the zombies' make-up, since he was known at least in part for his ability to make up whole groups of actors/extras at speed, as per his work on the party scenes in JEZEBEL (1938), or on the cavalcade of beaten-up sailors and ne'er-do-wells in THE SEA WOLF (1941), with Time Magazine for example dubbing him "Chief Scar-Maker" on the latter picture (in its 4th April 1941 edition).

But as far as I know, there's no evidence about precisely what Axzelle's contribution to WHITE ZOMBIE was.