Opus can pass files to 7-zip and WinRAR via command line, e.g.
"/programfiles\7-Zip\7z.exe" t {filepath}
XML
<?xml version="1.0"?>
<button backcol="none" display="both" label_pos="right" textcol="none">
<label>7z Test</label>
<function type="batch">
<instruction>@nodeselect</instruction>
<instruction>"/programfiles\7-Zip\7z.exe" t {filepath}</instruction>
<instruction>pause</instruction>
</function>
</button>