What if he’s Zac’s arch-nemesis? He’s just cartoony enough to fit with the hero motiv Zac has. The old lore lists them as friends, but I doubt Zac would like someone who shoots whoever crosses into his domain.
They are also both results of the illicit science Zaun uses. One uses his powers for good while the other uses it for evil.
And let’s be real here, Twitch would fit right in as a Saturday-morning cartoon villain.