Как заменить диагональ матрицы нулями? (tasm) - Assembler

Data    segment
s   db "Martica A:",10,13,10,13,24h
A   DB      1,1,2,4
    DB  2,5,2,2
    DB  3,3,-3,4
    DB  5,5,6,-7
data    ends    
 
code    segment 
    assume  cs:code, ds:data
start:      
    mov ax, data
    mov ds, ax
    mov cx,4
    mov si,0
 
m1: push    cx
    mov     cx,4    
m2: mov ah,a[si]
    mov al,0
    cmp ah,al
    jg mus
    mov ah,0
    mov a[si],ah
mus:    inc si
    loop m2
    pop     cx
    loop    m1
    mov     ax,900h
    mov dx, offset s
    int 21h
 
    mov cx,4
    mov si,0
 
m3: push    cx
    mov     cx,4
    
m4: mov     ah,2h
    mov     dl,a[si]
    add dl,30h
    int 21h
    
    mov ah,2h
    mov     dl," "
    int 21h
        
    inc si
    loop m4
    pop     cx
    mov ah,2h
    mov     dl,10
    int 21h
    
    mov ah,2h
    mov     dl,13
    int 21h
    
    loop    m3
    mov ah,0
    int 16h
 
    mov ax,4c00h
    int 21h
code    ends    
    end start