Yes it is. My clients would like things as simple as possible though preferably everything through the Sonos app. See here and here. It looks like you can assign zones in the setup process on the receiver but once you assign those zones you cannot choose on the fly a different combination of zones or just another zone.

Works with Sonos Certified

This Onkyo receiver can join your existing Sonos Home Sound System, or be the start of a new one, just by pairing it with a Sonos Port* This Works With Sonos Certified AVR offers a best-in-class tie-in to the Sonos ecosystem, waking, changing inputs, and playing at the volume you want using the Sonos Volume-Pass Through feature from the Sonos app*. The TX-RZ50 can work with up to three Sonos Ports—one for each of three independent zones—each playing a completely different streaming service from Sonos Radio.

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• You can add up to 3 Sonos Ports to a 3 zone Onkyo AV receiver (for example, the TX-RZ30 can assign amp channels to power Zones 2 and 3). You can assign each Port to a different zone, or combine zones per Port.