shell script to find and replace words line by line : I have a file consists of hundreds of records like this

    100,502030,0,444,RSVYU,10
    101,501412,1,555,DDGTH,11
    102,502269,0,222,DDERF,60
    103,508877,2,111,SDEFV,23
    


How can I use shell script to replace the value of the 4th column with 000 if the value of the 3rd column is 0.