"Can a player activate "Zombie Master's" effect when there are no Zombie-Type monsters in either Graveyard, discard a Level 4 or lower Zombie-Type monster and then target it with the effect?"
Answer:
Yes they can.
The same also applies to "Fossil Excavation". A player can activate "Fossil Excavation" while there are no Dinosaur-Type monsters in their Graveyard, discarding a Dinosaur-Type monster that they will then target with the effect.
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Curtis Schultz
UDE Netrep
CurtisSchultz_Netrep@hotmail.com