Here it is....
-system.. every tick
-----System compare to variables
-----------1000 / (distance (player1.X,player1.Y, player2.X,player2.Y)) > 1
--------------------System set layer scale to 1
-----System compare to variables
-----------1000 / (distance (player1.X,player1.Y, player2.X,player2.Y)) < or = 1
--------------------System set layer scale to 1000 / (distance (player1.X,player1.Y, player2.X,player2.Y))
Also set both all players to have the scroll to behavior.
You can make the 1000 any number you want as a min distance between players.
This will scale the layer that the players are on to a percentage relative to the distance between them. If the percentage is 100% or more of the minimum distance the the scale will be 100% or in this cause just 1.