When you use a monster with an original ATK of “?” then “Great Maju Garzett”’s ATK is zero.
Netrep Rulings:
“Great Maju Garzett” only receives its change in ATK when it is Tribute Summoned.
If “Great Maju Garzett” is not Tribute Summoned, it will remain at 0 ATK.
If “Great Maju Garzett” is Tribute Set, it will not change its ATK value.
If “Great Maju Garzett” is flipped face-down, it will reset its ATK value to 0.
“Great Maju Garzett” doubles the original ATK of the monster Tributed for the Tribute Summon. It does not check current ATK.
If “Great Maju Garzett” attacks “Cat’s Ear Tribe” and is not sent to the Graveyard, “Great Maju Garzett’s” ATK will be 0 after the Battle Step resolves.
If “Great Maju Garzett” is Tribute Summoned by Tributing a “Twin-Headed Behemoth” that has been Special Summoned by its effect, the ATK of “Great Maju Garzett” will be 3000.
If “Skill Drain” is active when “Great Maju Garzett” is Tribute Summoned, “Great Maju Garzett’s” ATK will remain at 0. If “Skill Drain” is activated after “Great Maju Garzett” has been Tribute Summoned, “Great Maju Garzett’s” ATK will become 0. If “Skill Drain” is negated or leaves the field, “Great Maju Garzett’s” ATK will remain 0.