best route to Zihua

I drive a normal speed as to not attract attention from The Federal ( find any excuse for a bribe ) Police ,with a trailer 3 days would be a good time and You could enjoy the scenery . The highway from Queretaro to Morelia is well marked ,I just don't remember the # ,the sign will say ,Morelia Cuota ( toll rd )
I have driven it so much that I never use a map anymore !