inside any cave or dungeon
Yes, Lucario is able to learn Dig. It can learn it through the use of the Dig TM.
Zigzagoon wouldn't be able to learn Dig by leveling up. You will need to give it the TM Dig to teach Zigzagoon.
You get TM28 Dig from the Fossil Maniac's brother on Route 114.
you can get 28 dig on route 114
the TM dig is found in the Pokemon maniacs house on route 15
Dig is a TM, so you can teach it to it at any level.
That TM is given by a kid in the fossil maniac's house which is west from fallarbor town.
Other Pokemon do know dig without the TM dig. Most DIGlets know dig. Find diglets in Diglet cave. Hope this helps!
the dig masters house in the town by all of the ashes. sorry name slipped my mind
Zigzagoon can be taught Dig at any level once you have TM 28. TM 28 can be found in Route 114.
go to the fossil maniacs house and talk to the little girl
In all Pokemon games, Riolu can learn dig with the TM Dig. If you have the TM Riolu should be able to learn it.