A bit simplified it's like this:
SoldierZoomSensitivityAll*SoldierZoomSensitivity4x00*(atan((vres/hres)*UniformSoldierAimingCoefficient*(tan(FOV/2)))/atan((vres/hres)*UniformSoldierAimingCoefficient*(tan(AimFOV/2))))
There's a few conditions to this;
SoldierZoomSensitivityAll*SoldierZoomSensitivity4x00 can not be above 3 or below 0.1. If it is, 3 or 0.1 will be used respectively.
If UniformSoldierAimingCoefficient is 0, the formula is slightly different.