Int 2F Fn 121E  U - Dos 3.0+ Internal - Compare Filenames                  [D]

   AX = 121Eh
   DS:SI -> first ASCIZ filename
   ES:DI -> second ASCIZ filename

Return: ZF set if filenames equivalent, ZF clear if not

Note:  supported by DR DOS 5.0+

See Also: AX=1211h,AX=1221h