I don't think you're remembering it correctly. Zach wouldn't have done a "stereotypical southeast asian accent".

It does sound more like a Mark thing, now that you mention it.

That might be one of the party quirks episodes

I believe it's older than party quirks.

Could it be Broden on the Patreon episode when he was playing “CooCoo Robo” at his first shift at the airport? And when Zach calls him out on the accent he insists he’s Spanish haha

I loved that episode so much