There were four books in the “Zanthar” series by Robert Moore Williams — Zanthar of the Many Worlds (1967), Zanthar at the Edge of Never (1968), Zanthar at Moon’s Madness (1968) and Zanthar at Trip’s End (1969) — but as far as I can determine, only the first, third, and fourth volumes had cover art by Jeffrey Jones. I’ve posted two of Jones’s “Zanthar” covers previously on RCN at a smaller size; now here are all three covers, re-scanned where necessary, and displayed in order of publication:
[CLICK IMAGES TO ENLARGE]