Hi @Sergei,
Welcome to the Zoom Developer Community. We are happy to help you.
At the moment our APIs are designed for pre meeting and post meeting operations only. Which means that the feature you are requesting is currently unavailable via our apis.
You can consider using one of our SDKs if you want to implement the muteAll feature. Here are links to our Andriod and JS Web SDK muteAll features.
To find all of our SDKs, please visit: https://marketplace.zoom.us/docs/sdk/native-sdks
Let me know if you have any additional questions.
Thanks,
Ojus