The Zapier trigger for Updated Moderator Tags is fantastic and I make robust use of it for multiple use cases.

I also use Moderator Tags as a simple way to build custom reporting (ex. question type: how to vs troubleshooting, who marked the answer: admin or superuser or other user). 

I shared some lessons learned around this in this post: 

What the post (and replies) highlight is the need to know what changed with moderator tags. The current version provides the current state of tags after something has been added/removed. 

It would be even better if the data provided by the webhook/zapier trigger indicated what was added/removed. It would make my post above obsolete and allow for more direct targeting of subsequent automated actions. 

I can also imagine use cases for multi-moderator teams wanting to set up automations of track when certain tags are added/removed and by whom.