There are a few ways you can go here.
1. Rejoin domain
If you can rejoin the pc back to the domain, you can then use an account with domain credentials to give ZZZ administrative rights.
2. Reinstall windows
An obvious answer is to wipe everything and start over.
3. Hack your way into the system
It is possible to hack your windows system and grant your user administrative rights. In order to do this, you will need to boot using a windows installation medium. This can be windows 7 or windows 10.
From the setup, open a command window (SHIFT-F10) and execute the following command:
copy c:\windows\system32\sethc.exe c:\windows\system32\sethc.exe~
copy c:\windows\system32\cmd.exe c:\windows\system32\sethc.exe
Reboot your computer and make sure you end up at the logon screen. If it automatically logs you in, log out first.
Now press shift 5 times to open a command prompt.
From here, you can use the following command to gain administrative privileges:
net localgroup administrators ZZZ /add
From here you can also reset your password or create a new user.
Don't forget to boot back into the windows setup and execute the following commands from a command window:
copy c:\windows\system32\sethc.exe~ c:\windows\system32\sethc.exe
This will restore the sticky keys functionality and patch the security vulnerability we created.
EDIT: Just to clarify, this only works for windows 7. Windows 8 and 10 have different methods that works nearly the same but this specific instructionset on option 3 will not work.