Factorise. (i) `4p^2 - 9q^2` (ii) `63a^2 - 112b^2` (iii) `49x^2 - 36` (iv) `16 x^5 - 144x^3` (v) `(l + m)^2 - (l--m)^2` (vi) `9x^2y^2 - 16` (vii) `(x^2 - 2xy + y^2) - z^2` (viii) `25a^2 - 4b^2 + 28bc - 49c^2`