The planned deployment schedule is as follows:
No service disruption is expected for this release.
Release Notes for release 258 will be published under Zuora Release Notes after Sandbox release. Release status and release notes link will be posted as this article comments.
Release 258 was deployed to EU and US Production successfully.
Here is the Zuora for Salesforce (Quotes) release note https://knowledgecenter.zuora.com/A_Zuora_Release_Notes/BA_Zuora_for_Salesforce_Quotes_Release#Maintenance_Release_9.18_(Release_Date:_2019-09-23)
Here is the Zuora billing release note homepage https://knowledgecenter.zuora.com/A_Zuora_Release_Notes
Here is the Zuora billing R258 release note https://knowledgecenter.zuora.com/A_Zuora_Release_Notes/A_Zuora_Billing_Release_Notes/22_2019_New_Features/18_Zuora_Billing_Release_258%2C_October_2019
When will the updated release notes be published for this release?
Our SF Sandbox had Zuora CPQ 9.18 and this is not listed on the release notes you posted above.
I see now that the details for 9.18 are in the link labeled 9.16. Just the top page needs updating.
Release 258 was deployed to EU and US Sandbox successfully.