Zello For Work users can install a SiteCast gateway to connect virtual Zello channels with real broadcast radio channels.
Alternatively, any Zello Windows user can purchase Radio-Tone's Zello-compatible RoIP1 Radio-over-IP controller. This small box uses a USB cable to connect 2-way radio audio with Zello or other audio application. They cost about $415 and it works with the free Zello app. Zello does not sell or support the device.
Radio-Tone RoIP2 videos:
Channel showing gateway in use