ZENworks Service Desk 23.3 is available only through Online Product Upgrade channel. To update to ZENworks Service Desk 23.3, deploy ZENworks Service Desk 8.3.x, and then update to ZENworks Service Desk 23.3.
To deploy ZENworks Service Desk 8.3.x, see the Appliance Deployment section in the Service Desk Appliance Deployment and Administration Reference.
To update to ZENworks Service Desk 23.3, see Section 4.1, Migrating to ZENworks Service Desk 23.3.