Spray a bit of WD40 into the gaps to help in lubricating the surfaces use a vise grip plier to hold onto the driver bit and another on the shaft that fits into the drill. Slowly torque the shaft left and right to help in getting the WD40 deeper into the gaps. Once you feel you’ve gotten enough in now pull them apart using the vise grips.
If that fails post a picture of what you’ve got now assuming you got one part off.