The Mamba Zombie was the disguise of a henchman of Roger and Lila. He appeared in "Mamba Wamba and the Voodoo Hoodoo", an episode of The Scooby-Doo Show.
The zombie had a pale white complexion. He wore a dark pink ragged shirt, another shirt that is brown underneath, and grey pants. He had yellow pupils against black sclerae, almost resembling black eye sockets.
The Scooby-Doo Show
All of them were trying to trick the band into signing over rights to their new song.
Some of the case was shown (including the unmasking) on Daphne Blake's webshow when AlexSuperFan2112 asked her whether the gang was responsible for the break-up of the band.