head to head
Neither is simply harder - they are hard in different places. Grand Theft Auto V demands more reads; Zenless Zone Zero demands more optimization.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.

Optimization · Practiced Mastery
A stylish urban gacha action RPG mixing combo combat with character-pull economies.
Grand Theft Auto V leans Execution (Practiced Mastery); Zenless Zone Zero leans Optimization (Practiced Mastery).
Zenless Zone Zero leans a little harder on execution, though the gap is small.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Zenless Zone Zero
Parry timing, dodge counters, assist-switch combos
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Zenless Zone Zero
Enemy patterns are scripted, not adaptive
Zenless Zone Zero leans clearly harder on variance.
Grand Theft Auto V
Some mission and lobby randomness.
Zenless Zone Zero
Gacha pulls and disc-drive substats gate power
Zenless Zone Zero leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Zenless Zone Zero
Team synergy, rotation theory, and stat optimisation dominate endgame
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.