Cadaverous Appearance. While it is lying still, the zombie dragon is indistinguishable from a rotting corpse. It can still be detected by the detect evil and good spell, or similar magic

Undead Fortitude. If the zombie dragon is reduced to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the zombie dragon drops to 1 hit point instead.

Multiattack. The dragon makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 16 (2d10 + 4) piercing damage

Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 4) slashing damage.

Rot Breath (Recharge 5–6). The dragon exhales lightning in an 60-foot line that is 5 feet wide. Each creature in that line must make a DC 15 Constitution saving throw, taking 18(4d8) necrotic damage on a failed save, or half as much damage on a successful one.