EVs: 252 Atack, 128 def, 128 Sp. Def
Item: Assault Vest/Normalium Z
- Heavy Slam
- Hammer Arm/Earthquake
- Dragon Tail/ Stockpile
For Guzzlord, I recommend physicals sets instead of special ones not only due to the higher Attack, but also because it's physical movepool is stronger and more varied on top of it; There are better Dragons to take advantage of Draco Meteor, and being at -1 Sp. Attack instead of -2 isn't going to help you out very much, since you're still better off switching. Payback has 100 BP before STAB if Guzzlord moves last, which is going to happen very often since it's such a slow Pokemon. If your opponent switches into a fairy-type, Heavy Slam is the move of choice since Guzzlord is also a very heavy Pokemon-- It has 120 BP under most conditions, which means it has the same amount of base power as Crunch or Dragon Claw do after STAB (80 x 1.5 from STAB = 120.) That also means if Payback isn't a good move to attack with, Heavy Slam would fulfill either of those two move's basic roles, so they'd be somewhat redundant to use. Hammer Arm and Earthquake are both great coverage moves, with the choice between the two depending most on what you want to hit hard. Dragon Tail can be useful for its ability to meddle with your opponent's switches (Payback doesn't have full power against switches) or otherwise prevent your opponent from setting up; Guzzlord doesn't mind the move's decreased priority, so there isn't really much to lose. Stockpile on the other hand can be useful since Z-Stockpile fully restores its HP on top of boosting its Defense and Sp. Defense by 50%. If it gets to +3/+3 Def/Sp.Def with full HP, it can be tough to take down.