Hello,
You can use the Hybrid example application for overlapping 802.15.4 and BLE communication (KW40Z_Connectivity_Software_1.0.1\ConnSw\examples\hybrid\ble_802_15_4_dual_mode_demo). XcvrInit states which mode will be initialized first. As you can see in the example, 802.15.4 PHY is also initialized in Phy_init().
BR,
Alex