Killer (Edens Zero) vs Zani: who would win?

Zani favored — Slight edge (~55%)

Killer (Edens Zero) · Edens Zero · Base

Tier
5-A
Attack Potency
Large Planet Level
Speed
High Hypersonic, up to Massively Hypersonic+
Durability
Large Planet Level

Zani · Wuthering Waves · Base

Tier
5-A
Attack Potency
Large Planet Level
Speed
Sub-Relativistic+
Durability
Large Planet Level

A heuristic estimate from normalized VS Battles Wiki stats: tier, attack potency, speed and durability.