combination of two point lists

Hi All,

A have a simple question about sorting values and points.
I have two lists (coming from the same csv file) the one "List a" contains points along the x-axis (also negativ x axis) , the other one "List b" along the y-axis( also negativ y axis).
Now I wanted every point from the List A along each point point from the y axis.

I thougnt I can simple construct the points but it needs long time and crashes my computer, the data inside contains 6000 items.
Does anybody have an idea and would help me ?

would be awsome !!!!
Thank you !
Best,
Leonie