how to remove the Zigbee stack using X-CTU from Xbee series 2

We are using Xbee series 2 modules for our project to proceed we need to remove the ZigBee stack using X-CTU first and then use just 802.15.4 specs. Please help

You can’t. you would need a series 1 module for that.

The XBee ZB or S2 modules are a Zigbee Enabled product only. You must use the XBee S1 or 802.15.4 modules for an 802.15.4 network.