Dear law and order situation is not too good in these areas, if you are going here for a road trip, then I will not suggest you to visit these areas. Otherwise, if you have any relations with the locals of Quetta or pashto speaking, you can easily roam around these areas with them.
I will suggest you the shortest route which is Multan-Muzaffargarh-Dg Khan-Fort Munro-Rakni-Loralai-Quetta.
Road is under construction from Muzaffargarh till Fort Munro, rest its fine !
The other route is very very lengthy, and will not suit you.