INT 61 - OPTIMA 1024 VGA-Sync - SET ZOOM WINDOW
        AX = 0006h
        BX:CX -> zoom window description (see below)
Notes:  width of zoom window must be a multiple of the pixel replication
          factor
        INT 61h is the default interrupt; the actual interrupt number can be
          obtained by calling INT 16/AH=FFh
SeeAlso: INT 61/AX=0000h"OPTIMA",INT 61/AX=0001h"OPTIMA"

Format of zoom window description:
Offset  Size    Description
 00h    WORD    X start of zoom window
 02h    WORD    Y start of zoom window
 04h    WORD    X end of zoom window
 06h    WORD    Y end of zoom window