Zigbee instead of Wifi

Is it possible to replace entire radio layer (Wifi) with a Zigbee layer n still use the core.
It might not be internet connected but can we use it as inter node communiocation.
We can have a structure of slave node and one master node with wifi for internet connectivity.

You might want to check out this thread: https://community.spark.io/t/nrf24l01-library-porting/2286/98

No, it’s not possible. But I have something in the works that will do exactly what you’re after, just not with Zigbee. I’m hoping to have it released by this summer.