It is much more than just converting it to ethernet. A usb to ethernet would require you to load a driver to the printer which is unlikely. The cables won't connect anyway both the USB for ethernet and the printer are designed to plug into a computer not each other.
You only hope is some form of print server. Many routers support attaching printers directly to them. The big issue will be zebra stuff has always been a pain. Since it like to run its own print format you need special drivers. You would have to be sure the router supported them. Otherwise you are going to have to find a dedicated printer server that support zebra printers.