index_first_row_zero = sum( cumprod(logical(YourMatrix), 2), 2) + 1;
Note: in the case where none of the entries are 0, this returns one more than the width. You did not define the desired output for this case.
index_last_nonzero = size(YourMatrix,2) - sum( cumprod( ~logical(YourMatrix), 2, 'reverse'), 2);
Note: in the case where all of the entries are 0, this returns 0. You did not define the desired output for this case.
