You've determined that the audit table in the itcc database is incredibly large, beyond comfort.
This isn't actually a problem and is the result of normal operation over a long period of time. The audit table contains every instance where a user has logged into Zephyr, logged out of Zephyr, and deleted data from within Zephyr. This includes every time an external service or application completes these actions via the API.
If your external applications are consistently interacting with Zephyr, it's good practice to make sure these tools are staying persistently logged in over a longer period of time. If your tools are logging in to complete a single action then logging out, the audit logs can build up and become quite large.
If you're OK with not having this data from time to time, you can truncate the itcc.audit table by logging into the Zephyr database and using the TRUNCATE TABLE [tablename] command where [tablename] is itcc.audit. Afterwards, make sure to OPTIMIZE the table as the database engine will need to reclaim some space on the system.
If you're curious as to the exact contents of this table, you can view it in a friendly format at http://[yourzephyrserver]/flex/assets/html/auditlog.html.