I am not sure what is your question here.
It is not possible for me to give a general solution for this, as it depends on how you have set up the series mappings. However, I believe that extracting the selected x and y values is possible and it is SeriesMapping-specific.
For instance, if you know that you x values range from 50 to 150 and in the zoom event handler the xScale is 2.0 and the xScrollOffset is 0.25 - then the selected x range is [75, 125].
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