ZZZ Endgame Explained: Shiyu Defense, Deadly Assault, Hollow Zero

Zenless Zone Zero‘s endgame is not one mode you grind forever — it splits into three separate systems with three separate entry requirements, and picking the wrong one for your roster is the single biggest reason players stall out after finishing the story. This guide breaks down Shiyu Defense: Critical Node, Deadly Assault, and Hollow Zero exactly as they work in version 3.1, “The Long Goodbye,” and tells you which one actually fits how many agents you’ve built, not which one has the shinier reward screen.

Once the main story wraps, Zenless Zone Zero funnels players toward a small set of repeatable, high-difficulty combat modes designed to test built rosters rather than story-mode power. These aren’t formally labeled “endgame” by the developer, but the community and most guides treat Shiyu Defense and Deadly Assault as the two headline challenge modes, with Hollow Zero sitting alongside them as the game’s permanent roguelike system. Each one asks something different of your account, which is exactly why choosing between them by roster size matters more than chasing whichever one pays out more currency this cycle.

The single biggest mechanical difference between the two headline modes is roster width, and it’s worth understanding before you commit a week of farming to either one.

Shiyu Defense: Critical Node

Shiyu Defense is Zenless Zone Zero’s primary Polychrome-generating challenge, and it works by splitting each floor into two separate combat nodes that must be cleared with two entirely separate teams of three agents. A guide covering the mode is blunt about the requirement: you need two separate teams of three Agents that cannot share characters. That single rule is what turns Shiyu Defense from “build one good team” into “build two good teams,” and it’s the wall most players hit first after finishing the story. The mode currently runs across five frontier sections rather than the seven it originally launched with, following a difficulty pass in an earlier version.

Deadly Assault

Deadly Assault launched later, in version 1.4, as a permanent high-risk combat mode built as an enemy simulation tied to Hollow Zero’s systems. Deadly Assault is designed to simulate high-Ether activity combat scenarios, focusing on highly dangerous hostile entities, and each session features three high-risk entities, with their weaknesses and resistances revealed in the challenge details. The important part for anyone still building a second team: Deadly Assault uses a single team of three Agents rather than two, so it is more accessible for players who have one strong team and are still working on a second. That doesn’t make it easy — it’s routinely described as a step up in raw difficulty from Shiyu Defense — but it doesn’t demand roster depth the way Shiyu does.

Hollow Zero is the odd one out because it isn’t gated by the biweekly schedule at all. Hollow Zero is the roguelike game mode in Zenless Zone Zero, comprised of six regions with different difficulty levels, and once you start a session you must explore several HDDs and combat waves of enemies in exchange for rare rewards. Inside a run you collect Resonia — temporary buff cards that stack into a build for that specific attempt — plus Lost & Found items and Combat Configuration upgrades that carry over between runs, unlike Resonia which resets each mission. Zones are further split into escalating difficulty tiers, so a single region can be run at multiple power levels depending on how much risk you want to take on.

Both headline modes run on the same clock, and that clock is what decides what you should actually be leveling up on any given week. Both modes reset every two weeks on Friday, alternating with each other. In practice that means if Shiyu Defense is live this cycle, Deadly Assault is dormant until the next Friday reset two weeks out, and vice versa — you never have both active at the same time. That rotation is exactly why the question “what should I build right now” has a different answer depending on the week: if Deadly Assault is up and you only have one solid team, that’s your target; if Shiyu Defense is up, it’s the week to lean on both squads you’ve built, even if the second one is rougher around the edges.

For the deeper mechanical breakdown of each individual mode — floor layouts, buff selection, and stage-by-stage notes — a dedicated Zenless Zone Zero endgame breakdown is worth bookmarking alongside this overview.

This is the part most newly-arrived endgame players get backwards. It’s tempting to keep dumping resources into your best team — maxing skill levels, chasing a perfect Drive Disc set, pushing a signature W-Engine to its ceiling — because that team already clears content and feels rewarding to improve. But Shiyu Defense doesn’t care how strong your best team is if you can’t field a second one; the mode structurally requires two non-overlapping squads, so a maxed single team caps out at half the mode. Deadly Assault is more forgiving on paper, but its rotating boss weaknesses and resistances still punish a roster with zero backup options when the season’s target counters your only built team.

The actual ceiling on your endgame progress isn’t how deep any one team is built — it’s how wide your usable roster is. A six-star skill upgrade on an agent you already clear content with is a small, incremental gain. A second functional team, even a mediocre one, is what unlocks an entire mode you were previously locked out of. If you’re choosing where to spend Polychrome pulls, Dennies, and upgrade materials this cycle, breadth beats depth almost every time at this stage.

“Deadly Assault is easier than Shiyu Defense”

Not quite — Deadly Assault is more accessible in terms of roster requirements because it only needs one team, but multiple guides describe it as a meaningful difficulty step up from Shiyu Defense once you’re actually in the fight, with tighter mechanics and less room for a mismatched team composition. Accessible entry point and easy fight are not the same thing.

“Hollow Zero doesn’t matter for endgame”

Hollow Zero gets treated as a side activity because it isn’t on the biweekly reset clock, but it’s the only one of the three modes you can always play, and it’s a real source of Investigation Points and License Level progress that feed back into account power over time.

“You need every character to be S-rank to clear Shiyu Defense”

The two-team requirement is about coverage, not roster rarity. A team built around solid A-rank agents that fills a role your other team lacks is worth more toward clearing Shiyu Defense’s second node than a third copy of the same S-rank archetype you already have covered.