Route pattern /cms/contents/{cms_menu}/{{cms_menu}} cannot reference variable name cms_menu more than once. code example

Example: Route pattern cannot reference variable name more than once. laravel

When you define a route as a resource then Laravel seems to create all the
  routes necessary for your resource: GET, POST, PATCH, DELETE.

So you would just need to define 
Route::resource('taxonomy','TaxonomyController'); 
or 
Route::resource('taxonomy.post','TaxonomyPostController');