XBee 802.15.4 and ZigBee modules are not compatible.
The Digi XBee 802.15.4 modules are the easiest to use, most reliable and cost-effective RF devices we've experienced. The 802.15.4 XBee modules provide two friendly modes of communication - a simple serial method of transmit/receive or a framed mode providing advanced features. XBees are ready to use out of the package, or they can be configured through the X-CTU utility or from your microcontroller. These modules can communicate point to point, from one point to a PC, or in a mesh network. And, all of the modules sold by Parallax are compatible with one another!
Because the XBee modules have 2 mm pin spacing, we recommend one of our adapter boards for each module. Our adapter boards provide several advantages to the XBee modules such breadboard-friendly standard 0.1 inch pin spacing, mounting holes, and easy-to-solder connections. Even if you are communicating point-to-point without a PC, we still recommend that you always have at least one XBee USB Adapter Board (# 32400) so you can easily configure and test each XBee module prior to putting it in a point-to-point application.
Cross-compatibility with other 802.15.4 XBee modules
Low-power sleep modes
100 ft (30 m) indoor/urban range and 300 ft (100 m) outdoor line-of-sight range
Configured with API or AT commands, local or over the air