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Anonymous great explanation but you need to provide sample pbix file, not sure why you cannot do that.  With all the details you mentioned, you didn't mention what is going to be on the x-axis of the line chart, understood that the Y and Y2 line is based on the left and right slicer.

 

I can tell you on top of my head, you need two calendar table, one for left, linked with you data table, right date dimension, not linked with anything, it is purely for slicer and then used in measure. Now, this measure depends on what you will be using on the x-axis, it is not at all clear, for example, left slicer filtering Jan/Feb/Mar and Right Apr/May/Jun, now what is superimpose in this case? 

 

In nutshell, enough details provided but no detail how you are consuming it and what suppose to be output (in my opinion), I could be wrong here.

 

So a sample file with expected output will help to get the solution. Help us to get help.