Did you run that Certbot command on the server that hosts dev-classroom.zunuzi.com? I will assume so.
There is an A record in the public DNS for that domain pointing to an EC2 instance.
But, right now it cannot be reached from the public internet on port 80 or 443 (http or https). So, I can't tell anything about what is running there.
Certbot has no record of current certs but another ACME Client may have been used. Or, even a cert gotten somewhere else and manually copied here.
We need to look at the service that would use that domain's cert. Do you know what is running on that server that uses the cert? Like Apache, nginx, or some other service? We can look at its config and see where the cert files are. From that path we can make good guesses about where they came from.
Or, just start it up and we can poke at it and possibly save some time 
Let us know what you can.