Not sure, I am suggesting PL_ALL draws it all.
PL_FINe only for the selected Asset.https://manual.zorro-project.com/plotmode.htm
Any plot command is normally linked to the current asset. When multiple assets are traded, only prices, trades, and curves linked to the asset selected with the [Asset] scrollbox are plotted; curves linked to other assets are only plotted when PlotMode got set to PL_ALL. For plotting parameters of different assets together, store them in different variables and then plot all together without calling asset() inbetween. For instance, inside an asset loop you can store them in a var array with one element per asset, then plot all elements of the array after the asset loop. The curves are then visible on the chart when you select the last asset of the loop and click [Result].
Not sure if it is right, since you don't post code.
You can draw something like that.
var equity = EquityShort+EquityLong;
plot(Asset,equity,MAIN,color(random(100), RED, BLACK, BLUE, YELLOW, ORANGE, PURPLE, MAROON, LIGHTBLUE));