Pioneer's card pool conveniently contains the vast majority of decks that I've had huge success with. While I've obviously been working on bringing versions of Jeskai Black and the like into Pioneer, it wouldn't make sense if I was working on those decks before the one that allowed me to win Pro Tour Amonkhet.
These cards are all legal and even have some excellent non-Zombie cards from older sets that help round out the archetype. However, we have to talk about why the Zombies themselves will eventually be a viable archetype in Pioneer in the first place.
Cryptbreaker is the backbone of the tribe and the reason to even consider Zombies in the first place. You could make a case for using Cryptbreaker as a way to discard cards for nefarious means and I'll get to that eventually. Using Cryptbreaker as the backbone of a disruptive aggressive deck is what I'm mostly interested in.
Not only does Cryptbreaker reward you for sticking to a tribe, but it's also a marginal opportunity cost one-drop that helps prevent flooding and gives you staying power against more controlling decks. Additionally, it allows you to load up on removal against aggressive decks and play the control role. It's one of the strongest one-drops an aggressive deck can possibly have because of its utility.
Diregraf Colossus is another fine payoff for Zombies, but it doesn't come online until much later. For the most part, it will be the way you lock up games where you're slightly ahead. Both Cryptbreaker and Diregraf Colossus demand removal spells immediately, which increases the odds that either one sticks and runs away with the game.
Finally, we have Dark Salvation. Pioneer already has plenty of removal options, especially in black, but Dark Salvation is among the strongest if you're able to use it. Early-game, it's weaker than Fatal Push, but by Turn 3 or 4, Dark Salvation will often kill whatever you want. Late-game, it's another mana sink. You can use it against opponents with no creatures and you can also use it against an opposing Turn 1 Cryptbreaker from your opponent. Overall, Dark Salvation is versatile and yet another way to deal with flooding.