If you want to make calls to Zone Manager you must to configure a Read-Only account for that Zone Manager within CenterScape first.
You can then use these credentials to make the API call.
In CenterScape, go to Admin Console>>Configuration>>Zone Managers and choose the Zone Manager you want to poll with API calls (unless you have just the Local Zone Manager, then you can only choose the Local Zone Manager) and put in the configuration settings for the Read-Only account.
A sample screenshot is below:
CenterScape: Read-Only Account Required For Zone Manager API Calls