You can use an external command line tool for unzipping your archive, see here for example. Put it in your [Files] section:
[Files] Source: "7za.exe"; DestDir: "{tmp}"; Flags: deleteafterinstall;
Then call it in your [Run] section, like this:
[Run] Filename: {tmp}\7za.exe; Parameters: "x ""{tmp}\example.zip"" -o""{app}\"" * -r -aoa"; Flags: runhidden runascurrentuser;
References
https://stackoverflow.com/questions/40704442/is-there-a-way-to-extract-zip-files-in-inno-setup-after-a-certain-page-is-done
https://stackoverflow.com/questions/6065364/how-to-get-inno-setup-to-unzip-a-file-it-installed-all-as-part-of-the-one-insta