Based on what I've read so far, this might not be possible or at least requires a the addition of a process that I'm not familiar with. Is it possible to automatically apply Gmail labels to emails that match a given search?

For example, I have a zap set up that automatically creates a Gmail label for each clio matter.(For some reason, though, on the web version of Gmail, they're nested under '/' which is nested under 'clio.' On the mobile version of Gmail they look like Clio/[matter number]-[client last name], which is how I intended them to look.) I have a separate zap that triggers when I send an email including a tag that includes the matter number. I'm trying to get it to apply the corresponding label to that email. Is this possible. I've seen a couple a threads suggesting using a Google sheet to record the labels. 

Any thoughts?