> Technically, 0% unemployment would mean that you can't take another job, as you transitioning into another job would create frictional unemployment

Transitioning to another job only creates frictional unemployment if there is a period where you are out of work but looking for work. Otherwise (e.g., if you find a new job before leaving) if you have a break from work as part of transition, it creates a frictional exit from the labor force, not frictional unemployment.

But 0% unemployment is hard to imagine if employers can terminate workers without first finding them acceptable replacement employment.