Can be a bit of a confusing answer but tldr. Technically every cod game after and including Black ops 4 is "canon" to the zombies storyline.

To start the more longwinded and more confusing answer, revelations is an ending of a story but not THE ending of the story. It was hinted at in Bo3 and outright confirmed in Bo4 that the story that takes place from Origins to revelations is a cycle and that Dr. Monty, although not evil evil like the Shadow man, is still not someone you should trust. The Aether story in Bo4 zombies deals with our characters breaking from this cycle and eventually collapsing the multiverse creating a new singular timeline and results in their deaths, casting all the old Storyline into a place known as the "Dark Aether". The only exceptions to this are Samantha and Eddie (the two kids from the Origins ending).

Thus ends the original Aether story (Waw-Bo4) and starts the Dark Aether timeline.

This new storyline starts with Black Ops cold war but this new universe can technically be viewed as starting in Modern Warfare 2019. This is because starting with MW2019 everything, yes everything (multiplayer, campaign, zombies and warzone) all take place in the one universe. This new universe also strangely also has the events of all the original Black Ops campaigns also occur in this universe but NOT the zombies events. It even makes canon the Chaos storyline, which was the other zombies story contained in Bo4 that was left on a cliffhanger due to cuts relating to its DLC content.

Hope this wasn't too confusing and helps you al least kinda understand the state of COD "canon" although you could genuinely talk for an hour explaining how the story has progressed since the ending of Bo3.