This guide will let you know how to unlock The Sai in Col War Zombies.
You first need to go to the Zombies section and complete all the objectives in THE NUMBERS event. Go to Outbreak Survival, do all the objectives, and complete three multiplayer matches on the zoo.
And you need to earn objective milestones in Outbreak Survival. You also have to win the multiplayer demolition match or earn two or more zombie rounds or objective milestones and exfil successfully.
You will need to get 50 eliminations in multiplayer or slaughter medals, which kills five enemies rapidly.
Here, you have to get ten kills with lethal equipment or earn a lethal equipment medal, multi-kill medals in zombies. You will earn 25,000 total multiplayer or zombie essence.
After that, you need to make three multiplayer kills without dying or recover 500 health with food items in a region of Outbreak Survival three times. The zombies will also drop food after getting killed.
You also have to get five kills with scorestreaks in multiplayer or earn support multi-kill medals in Zombies. You can use the war machine to do it quickly.
After doing all nine of these, The Sai will be unlocked for you.
The next objective is that you need to get 5 kills with or assisted by your field upgrades in multiplayer or earn a field-grade multi-kills medal in Zombies.
Finally, you will need to earn three multi-kills in multiplayer or eliminate elite enemies in Zombies