I just
threw a .5 ohm atty on my Zmax, it just refused to fire and the display showed 0.5
I thought maybe it only threw error codes during a hard short, so I took a screwdriver and hard shorted the center pin to the side of the 510 connection, it just refused to fire and the display showed 0.0
So either Smoktech changed the chip (which is possible, my zmax is a bit old, I got it when the v2s with RMS first came out) or it's not a shorting issue you have. If it's not a shorting issue, I don't know what to say, I've never seen that before on my Zmax.
If it is a short between the 510 connection, the top cap of the zmax can be removed fairly easily if you have access to a vise or large locking pliers. The cap can just be pulled off, but be careful not to yank the cap far away from the
device when detached, as you will break the wire that leads from the center pin to the circuit board.
Once you have the cap off it should be very easy to replace the rubber boot around the center pin. You could probably do it with the cap on, it would just be more of a hassle.