Konami recently sent us a ruling reversal for "Zombie Master" that involved activating its effect while there are no Zombie-Type monsters in the Graveyard.
The new ruling is as follows and will be added to the FAQ:
"You cannot activate "Zombie Master's" effect if there are no Level 4 or lower Zombie-Type monsters in the Graveyard, even if you would discard one to activate the effect."
Curtis Schultz
UDE Netrep
