If you are running Zencastr at the same time as Skype/Hangouts/etc so that you can have and/or record video during the call, then we recommend that you have each participant mute their audio in Skype/Hangouts and have all of the audio routed and recorded only through Zencastr.
If you are using third-party VoIP software to enable you to record a backup of the Zencastr audio then you should turn Zencastr's built-in VoIP off in the Audio Settings on the recording page. In this configuration Zencastr will still record you and your guests but it will not connect you in a live VoIP call with your guests. This is left to whatever third-party VoIP software you are using.
* WARNING - When you have Zencastr's built-in VoIP turned off, you will need to take extra care that everyones microphone are set up properly and that Zencastr is receiving their audio. Otherwise you risk recording only silence as you won't be able to hear them through Zencastr during the recording. It is best to leave the built-in VoIP on at first and make sure you can hear everyone through Zencastr without any other VoIP software running. Once you are confident that each mic is selected properly, then you can turn the VoIP off and start your recording.
You can also visually see that Zencastr is picking up your guest's audio by looking at their user card as the recording progresses. If all is well, you will see a green audio waveform build up on the bottom-right of the user card as you record like so:
Another simpler option for recording backups of a Zencastr recording is to use a program like Audio Hijack. It will allow you to record a backup of you and your guest on separate tracks without the need for an additional VoIP program like Skype/Hangouts/Zoom.
If you are using Audio Hijack, you will want to configure your recording in Audio Hijack like so: