What is the best material for premolar's crown after root canal: zirconium, silver-palladium, gold, etc fused porcelain?

Crown materials. There is not one best material and many factors determine the material used.Factors include bite, amount of remaining tooth structure, cosmetics, oral hygiene, condition of the remaining teeth, skill of the dentist and the lab used. Discuss this with your restoring dentist.
All are good. I like a pressed ceramic crown that has layered porcelain on it and then this is bonded to the remaining tooth. E-max is one type crown. Zirconia and porcelain fused to gold crowns are also wonderful crowns.