Since the ZAK is retrieved from the API, I would recommend posting this in #api-and-webhooks so that one of my extremely knowledgeable colleagues can assist you with your usage of our REST API.
ZAK tokens will need to be refreshed by making a new request, if it’s over 2 hours since it was generated. To clarify, the 90 day expiration is specific to our custCreate user types, which is functionality that is exclusive to our ISV/API Partners.