Steve,
you mistake "Text Only" as having this literal meaning. It's more about "Generic". This printer driver means it forwards anything sent to it 1:1 to a printer at the configured Port (USB/PRT/COM/serial, whatever).
And my educated guess for ZPL is Zebra Printer Language. Which means the files you can print could be text mixed in with binary data. I'd guess (again) some ZPL commands would specify files names to print or creating QR codes of a string or other data, so there's no limitation to only be able to print text.
You should actually be more able to answer your own question, because from your initial post I get you have an assorted list of ZPL files. If you don't know what they are for, then the question I have is why do you even care for printing them.
All todays printers, also Zebra printers also allow to install a "normal" (GDI+) printer specific driver that allows using it with VFP reports. The endless paper rolls or labels and some other specifics require some other options than usual, but I have designed usual FRX reports for such printers that used a configuration option to automatically send a paper cut command after each report, and so you don't require to be able to send Zebra specific commands to a Zebra printer. Think mabout it more generally, any printer has some commnd language specific to it, some by more generally defined standards like Postscript, and printer drivers in general "hide" these languages and command from you and are therefore usable top print anything that Windows provides in the form of GDI+ - which stands for Graphics Device Interface and in short means anything you prepare is a graphic format (both vector for fonts/lines and pixel formats for images) and then the driver has to process that and forward it to the printer.
In essence you can do everything in both ways. If you're not at all familiar with Zebra Printer Language commands I guess you at least would have capabilities in designing VFP reports (FRXes) and then using the usual printer drivers would get you going easier than taking the learning curve and hurdle to learn printer commands that are also only specifically working for Zebra.
As far as I know the community of Fox developers the preferred method is printing directly, this comes from starting in old times where sending files to printers was the usual way, today you have printer drivers with more abilities, allowing you to, for example, use any true type font, design reports with graphics and have more of a visual preview of the printed receipt/label/whatever than with commands. Are you a DOS shell guy? Then sending out commands may be more for you? Are you a Windows user and have you designed VFP reports before? Then don't care about ZPL files and what commands they contain.
Chriss
