Is it "a_" instead of "z_"?
https://docs.splunk.com/Documentation/Splunk/7.3.1/Admin/Wheretofindtheconfigurationfiles
The finer points of lexicographical order
In the global context only, lexicographical order determines precedence. Thus, files in an apps directory named "A" have a higher priority than files in an apps directory named "B", and so on. Also, all apps starting with an uppercase letter have precedence over any apps starting with a lowercase letter, due to lexicographical order. ("A" has precedence over "Z", but "Z" has precedence over "a", for example.)
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