This looks like the bottom of another letter on the 'C' in Cent. Thought it could be a platting blister, but it's too straight. Plus a small die crack.
The cladding has already been breached under EN and at bottom left of the Memorial. It won't survive you anyway. Exposing the zinc on a Zlincoln to atmosphere is a death sentence; zinc enjoys reacting with things too much. I always wondered who thought up using a metal for coinage whose chief prior use was as a sacrificial anode.
Actually, in the closeup the lines running the same way as the whole of the feature tend to support the idea of a die gouge, and there's a ton of polishing lines around it hinting that they tried to remove it. So yeah, that's my working hypothesis about it now. Unfortunately, as I mentioned before, since it's a Zlincoln it's almost certain to corrode away over time. You'll probably be the only collector who ever gets to enjoy owning whatever feature it is.
