You have two options, either remove the ListUrl and let the Event Receiver fire for all the custom lists and inside your event through code check if the List is the one you want, then move on else ignore, something like:
if (properties.ListTitle == "MyCustomList1" || properties.ListTitle == "MyCustomList2")
If you want to check ID of the list, then
properties.ListItem.ParentList will give you SPList Object and then you can check
Or you can add other Event Receiver in same solution with ListUrl, make a separate class inside the solution, move your code logic in a function in this separate class, call the function of this class from both Event Receivers... To manage a centralized code!
I hope this helps