You can use the ^ID ZPL command to delete objects, graphics, fonts and store formats. These can be deleted in groups or selectively. Pag. 214. ZPL programming guide.
Another SGD command that you can use is "file.delete". You will need to specify directory and name with the extension. Pag. 729 ZPL programming guide
! U1 do "file.delete" "e:abcd.zpl"
For more information, please, review our ZPL programming guide, link below.