I also live near Isb Highway and used to visit Lahore once or twice in a month. One of my friend told me about mandra-chakwal route as well, but when i calculated distance on google maps,,, i didn't feel it as a good option. and the best option, in my opinion is still via zero point. Almost non-stop till toll plaza and then M2
Highway-Zero Point-Kalarkahar ~150 KM
Highway-Mandra-Chakwal-K,Kahar ~120 KM