If a vehicle gunner has used its fire control system to set a firing solution, the setWeaponZeroing command no longer has any effect, until the FCS zero is cleared by the gunner manually changing the zero.
This makes the command potentially inconsistent when used on vehicles equipped with an FCS.
Place a Slammer with a gunner to play as.
Get in the gunner's seat and find a distant target for reference.
Select the coaxial MG. (This isn't gun-specific but selecting the coax makes things easier to test)
Using the zeroing up/down keys, adjust the zero to be something other than 200m.
Run this code in the debug console:
player setWeaponZeroing ["LMG_coax","LMG_coax",1];
Observe that the zero is now set to 200m.
Now use the vehicle FCS rangefinder to get an exact range to the distant target and automatically zero the gun for it.
Run the code in the debug console again.
Now observe that the zero has not been changed and the FCS firing solution remains in place.
Fire a burst at the distant target, and observe the tracers indicating that the FCS solution really is in effect - if the zero had been overridden, the tracers would be way off.
See also https://feedback.bistudio.com/T85659 - addressing that by allowing FCS to be disabled would solve this, and addressing this to allow FCS to be overridden would allow a workaround for that one.