Hi. There is no official "pause" method. However, you can revoke your license (this will drop 1 day from license). It's up to you to decide whether it worth or not.
Note, your ZModeler have to be configured for online validation, so it can confirm license revocation. Until ZM confirms revocation, license is not put on hold and its time is running (you will see exclamation sign on license icon in account). Once revocation is confirmed, your license will show default icon in account (like on new license).