Kohler Generator 5E - Zinc Replacement

[bdfritz]

So I was doing my summer routine of doing the oil/impeller/zinc/spark plugs on my Kohler 5E Generator. Everything was fine... until I started loosening the Zinc Plug on the heat exchanger. The brass plug came off without any issues -- but the Zinc piece appears to be still stuck in there... any suggestions on how to 'loosen' it up to pull it out -- what's left of it?

Thanks!
Brian