Details from Salesforce: Salesforce instance AP1 will be migrated to a new site between 1:00 am AEST, Jun 18 (11:00 pm SGT, Jun 17) and 3:00 am AEST, Jun 18 (1:00 am SGT, Jun 18).
You can find more details about the maintenance schedule below on Salesforce Trust:
http://status.salesforce.com/status/AP1
The SF instance will be available in Read-Only mode during this maintenance window.
Impact on Zuora customers: For customers using Salesforce instance AP1, Zuora 360 Sync will be unable to sync the data to Salesforce during this maintenance window proposed by Salesforce. This will result error in sync history, so you might wish to switch off sync and have it turned back when the maintenance is completed.
Support Team
Jyoti_Sinha