I had a $6\times 6$ matrix
{{1., 0., 0., 0., 0, 0},
{0, 0.538752, 0.382352, 0.0788956, 2.35142*10^-7, 0},
{0, 0.121876, 0.449018, 0.405176, 0.0239311, 0},
{0, 0.0147839, 0.264751, 0.596752, 0.123713, 0},
{0, 0, 0.0294091, 0.381909, 0.563762, 0.0249205},
{0, 0, 0., 0., 0., 1.}}
and I wanted to multiply row 3 by 0.8, row 4 by 1.2 and divide each column by the sum of each column except the first and last column.
Instead of doing it manually by editing it on the matrix, is there an alternative or Mathematica code to do so?