Guiding Questions:
1. How does this card stand on its own (analyze the HP, attacks, Abilities, etc. of the card)?
Zekrom EX, like Reshiram, has an exceptional 180 HP. The attacks are similar to Reshiram EX, but its heavier attack discards two energy instead of recoil. This is both good and bad, as the lack of recoil makes a revenge kill much more difficult. However, discarding energy makes it harder to continue attacking, forcing either to discard a DCE and quickly replace with another, or discard two lightning and hope you can switch to another attacker or a free retreater to Dynamo into. On the plus side, there is no fighting pokemon that can reliable OKHO Zekrom without some sort of stipulation, either with a revenge kill from Terrakion, or a three energy Heavy Impact from Donphan, and Eviolite denies either of that unless the fighting pokemon can dig up a pluspower.
2. What role does/could this card have in the metagame?
Heavy hitter in ZPST and ZET, especially against Magnezone, which can give Zekrom trouble in the late game. I believe Zekrom will remain the main attacker in most Zekrom decks, but Zekrom EX can be used to take out key pokemon in an opposing deck's infrastructure, allowing Zekrom, which is already known for taking an early lead, to then finish off the rest of the pokemon. Eelektrik is essential in such a deck, however, as discarding the energy too often can be costly, and more importantly, Zekrom EX really needs to be able to attack the turn its put on the bench. Otherwise, there is too great a risk of it getting dragged out and KOed, especially in a Eelzone heavy meta.
3. What cards, if any, does this card combo with?
Eelektrik. It serves as both acceleration and energy recovery, which suits Zekrom EX just fine. Shaymin can also be used to move energy to Zekrom in a pinch.
4. Give it a rating (out of 10), and explain why you have given it that rating.
I'll give Zekrom an 8/10. Not taking recoil is very important I think for Zekrom, especially since 50 recoil would put it a pluspower away from an Equake KO, but I'm not sure how difficult setting up attacks will be after using Strong Volt. Switch and Shaymin and retreat work just fine in theorymon, but how it does in practice will ultimately decide how good Zekrom EX is for prolonged play.