1 zekrom ex
Pokemon = 18
3 rare candy
3 pkmn catcher
4 junk arm
1 super rod
3 pkmn collector
1 flower shop lady
T/S/S = 28
Energy = 14
This deck relies on the energy recovery ability of Eelektrik and the draw power of Magnezone to keep a constant set up. Mewtwo is a counter to other mewtwos while the thundurus and zekrom EX are the primary attackers. Magnezone then sweeps at the end of the game, lost burning energy to KO anything opposing it.
I would add 2 more primary attackers to ensure that you don't have to rely on Magnezone too much and risk running out of energy. Thundurus is a perfect starter, so one more would be a great addition. Either a regular zekrom or a zekrom EX would serve as another additional attacker.
14 is a excellent amount for the deck, but I'd swap out 2-3 of the lightning for DCE. Not only can Mewtwo use it, but so can zekrom EX. Discarding the DCE on zekrom when you attack means that the next turn you can just attach another DCE to hit for 150 again.
With Magnezone as your draw support, you can really take advantage of N, so I'd max it out to 4. With your junk arm maxed out, you should be able to safely go down to 2 switch. With super rod, you won't need flower shop lady. Maxing out your pokemon collector will ensure that you get a full bench early in the game. If you need any room in the deck, you can safely go down to 2 catcher. With so much hitting power, you'll rarely need to target something weaker.
You already have an excellent deck that should do very well at upcoming tournaments. After a few small tweaks, you should find that you run even more consistently!