You can only have one coordinator in a ZigBee network, which is the device that forms the network and move data to and from other media types, like WiFi or usb.
Your can have multiple routers, which is a device that retransmit packets to extend the network reach. Most mains powered device like smart plugs and the line are also routers.
Some coordinator usb dongles can be converted to a router with a firmware upgrade, but this only makes sense if you for some strange reason already have an extra USB stick laying around that have a router firmware available.
If that is not the case, then some kind of mains powered device is nearly always a better and cheaper option.