Zero is the latest Specialist character to be added to the roster of Call of Duty: Black Ops 4. She can be used in both the competitive multiplayer and in the Blackout mode, though her abilities can only be used in multiplayer.
To unlock Zero to use in Blackout Mode or to use her as a Specialist in MP you will need to progress through the first tier of the Contraband stream during the new Operation Zero event. This event has gone live on the PlayStation 4 as of this post and will go live on other platforms (Xbox Live & PC) at a later date.
Zero does bring some new tools to multiplayer for players to experiment with. She is primarily a hacker and disrupts enemies and their equipment. She has both a special issue EMP grenade and a weapon called the Ice Pick. The new Specialist can be accessed in Blackout from the Multiplayer character menu. She can also be accessed via the Specialist select screen in multiplayer once you’ve completed the first tier in the Contraband Stream.
Given that this Operation is named after the character there’s going to be plenty to unlock for Zero in terms of skins in Contraband stream. This Operation will last for 70 days and it features 100 Tiers. Not much seems to have changed regarding how fast the tiers are earned but they still seem to be tied to time played.
You can play either Blackout Mode or Multiplayer to earn credits toward completing tiers in Black Ops 4 to earn Zero.