Footnote for a quote containing a quote

Solution 1:

Multiple footnotes attached to the same place in the text tend to be confusing and are best avoided, even if they are not explicitly prohibited by whatever manual of style one is following. Moreover, in scholarly work, one is expected to make it clear in one's citations whether one has actually consulted a particular source oneself, or one knows about it only indirectly, through another source. In this case, it appears that the OP has consulted only one of the two sources involved: the one that contains the whole sentence that begins with 'As Leibniz'. The proper thing to do is, therefore, to have only one footnote, attached to that sentence as a whole, and in that footnote provide the bibliographical data about the source from which that sentence is quoted, followed by a word like quoting and then the bibliographical data for the embedded quotation.