Trampling Charge. If the mammoth moves at least 20 feet straight toward a creature and then hits it with a gore attack on the same turn in place of its bite , that target must succeed on a DC 18 Strength saving throw or be knocked prone. If the target is prone, the creature can make one claw attack against it as a bonus action.

Multiattack. The Zinngore makes two attacks: one with its bite and one with its tail. It can't make both attacks against the same target.

Gore. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 24 (3d10 + 7)  piercing damage and the target must make a DC 14 Strength saving throw or become grappled on the horns once a creature is grappled the Zenngore can't use this attack again 

Bite. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 7) piercing damage. 

Tail. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 7) bludgeoning damage.

When a creature enters the Zinngore's reach it can use its reaction to make a claw attack

Claw. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 7) slashing damage