The amass Zombies mechanic does not properly apply the creature type Zombie to an existing non-Zombie Army token. As per CR 701.47a, the existing token (e.g., an Orc Army creature token created with an amass Orcs effect) should become a Zombie in addition to its other types if it is not already. This is implemented correctly for amass Orcs (Zombie Army tokens gain the Orc creature type if an amass Orcs effect occurs), but is not implemented for amass Zombies. This prevents cards that should grant the Army abilities (Gleaming Overseer, Eternal Skylord, etc) from functioning properly. This error is also evident in the reminder text that appears when a card with amass is inspected: amass Orcs states "It's also an Orc", while amass Zombies does not. Amass Zombies needs to be updated to have its functionality match that of amass Orcs.