Print Label 4 / 6 for Zebra Printer

Hi Gurus,

I don't have much smart form experience, my client have requirement where there is already label designed and printing in Letter size and now they want to print same in 4 / 6 and for Zebra Printer.

How can i change Label, Letter size to 4/6 size? so that it prints in both Zebra printer and normal printer (In case of Zebra printer not available) ?

Thanks

SB