Probably the easiest, assuming your text file format is straightforward to decode:
filecontent = readtable('c:\somewhere\somefile.txt'); %readtable should be able to figure out the format on its own
filteredcontent = filecontent(filecontent{:, 3} == 0, :); %keep content where 3rd column is 0
writetable(filteredcontent, 'c:\somewhere\newfilename.txt'); %and save
