A 4-4 Eternatus line seems excessive, so I'd cut down to a 3-3 and bulk up Weavile, maybe even leaning into a secondary mode with Greninja+Zoroark and a bit more energy due to Weavile's flexibilty. This is a mild departure from what I think you're going for, but in this case, you could probably cut the Dark City and the Capture energy for three more copies of regular Dark.
Dark City and Hidden Dark Energy fulfill the same role, so it's redundant to have both, especially if you have Weavile to move everything, including the Hidden Dark Energy, around wherever it needs to go.
Additionally, you have some very fun tech as clarified by an official ruling, but if you use Devolution Spray Z on your only Eternatus VMAX, you are totally able to discard that Eternatus and deny prizes that way too, so you could also looking into playing a different version more centered around that with extra recovery cards.
This is definitely not advice I would take. 4-4 Eternatus is definitely a necessity (The thinnest line I've seen with or without Weavile was a 4-3) since your entire gameplan is based on setting up turn 2 and having another V Max on the field when the first one dies so you don't discard your bench. Greninja Zoro is a completely useless attacker and you would never, in
any single situation, rather use it instead of Eternatus.
While Dark City and Hide Energy fulfill the same purpose, they do it in different ways. Dark City is your Stadium bump option, and if Swell is out and you need to switch you get a secondary option in Hide Energy. And when you don't want to waste your manual attachment to retreat, Dark City is that secondary option. Also Weavile can't move Hide Energy because it's not a Basic Energy. Many players have been running both because it increases your number of options and outs without cutting into consistency or space.
Cut Piers and increase your other supporter counts. Crobat isn't like Shaymin where you can cut down your supporter counts because you have it. Only getting one Dark Asset a turn means you still need to dig for other board pieces. This means that Piers is just wasting your supporter for turn instead of just digging harder with Research, especially on turns where you have to Piers for Crobat. The only benefit is that you get to search Energy too, in which case you're better off running Spinners or just bumping up your basic Dark count, if not both.
Not that Weavile is very good to begin with, since you run 0 Energy acceleration and can set up a second Eternatus before the first one is KO'd, but you
could run the single Sableye V, which people including Tord have been running without Weavile. Sableye is able to take advantage of Zig pings without putting Eternatus in danger, and when you lose the flip, go second and have to Power Accelerator turn one (which might be less common with your list, as you run 4 basic Dark instead of the usual 7-8 ), then a Zig ping on top kills ADP and other Tag Teams. A second Zig ping on top of Power Accelerator kills V Maxes, which can be crucial in mirrors, since going second puts you at a horrible disadvantage otherwise. Weavile just means it's a little more useful late game too after you've potentially piled the pings onto something.
And in the case of going first, you want to bench Eternatus and attach. And in a
lot of matchups, including Skorch, ADPZ if they miss the T1 GX, the mirror if they don't Power Accelerator (and just attach manually to a benched Eternatus) you want to Boss and KO turn two. I keep preaching this to people learning Eternatus, but you want 4 Boss. Not just for turn two's sake, but most games where your opponent Stamps you is to prevent you from getting around either a one prizer or something you can't KO for game. I also think Eternatus lists not running Quick, Great,
and Comm are inconsistent lists. Of course with as much draw support as Eternatus runs, it's still an inherently consistent deck, but Eternatus relies so much on drawing hot that the entire deck should be built around it, hence running 3 different Pokemon search that aren't Piers (because once again, items that do the same thing as a Supporter are always better).
Black Market, Big Charm and Stamp are kind of contradictory to each other, and usually you see lists that run none of them. Black Market is usually viewed as bad because it's a dead card almost every game if your opponent can just dig and bump it. Big Charm isn't bad per se, but it cuts space from Comm counts, or more Supporters, or even more Energy. You get what I'm saying? It goes back to the whole "Eternatus should focus on being as consistent as possible, because that's how it wins games". And Stamp also isn't bad, but that's your third option as a cuttable card. Since every list runs 3-4 Marnie, you usually don't need to disrupt your opponent's hand any more than you already do. And running two is odd to me because Black Market and Big Charm are kind of working against it to give your opponent less prizes.
It's an okay list, but you should focus more on consistency and less on the long game with Eternatus since games shouldn't ever be taking that long unless you brick, which high caliber players and building it specifically not to.
