I have a Z-11 Pro at the base of a 16' aluminum pole sticking out from the balcony, with my 12-wide balcony railing as a counterpoise.
The Z-11 Pro finds a match on 40m, but _will not_ match on 80m.
One way to get around the "false tuning" problem with the Z-11 Pro would be to turn off the DC power to it when you ran VHF/UHF. Without DC power, it won't try to tune.
But don't try to make a silk purse out of a sow's ear. If you'll be tuning short antennas, you'll be happier with one of the SGC tuners designed to do that.
Charles