As Filip said, make maybe the top null and right null the drivers. Put this expression in the “Left” null position:
rightPos = thisComp.layer("Right").transform.position;
centerPos = thisComp.layer("Center").transform.position;
yMirror =rightPos[1];
xMirror = centerPos[0]-(rightPos[0]-centerPos[0]);
[xMirror,yMirror];
And this in the “Down” null position:
topPos = thisComp.layer("Up").transform.position;
centerPos = thisComp.layer("Center").transform.position;
xMirror = topPos[0];
yMirror = centerPos[1]-(topPos[1]-centerPos[1]);
[xMirror,yMirror];
End result: