I’m working with 900 .txt files which look like this:

[00000001]
aLETTIO
-----------------------------------------------------
[00000002]
mARIA cHARTE
-----------------------------------------------------
[00000003]
sIGRID
-----------------------------------------------------
[00000004]
lE tILL
-----------------------------------------------------
[00000005]
eMILIO
-----------------------------------------------------
[00000006]
rEINWALD
-----------------------------------------------------
[00000007]
dANDES
-----------------------------------------------------
[00000008]
dIGI―
-----------------------------------------------------

In Notepad++ pressing alt+shift+z will reverse upper and lower case, which is what I want to happen.

I would like to make a batch script so that I can process all files, rather than opening each and making the keypresses manually.

I failed to find anything searching StackOverflow.