You can output Joomla content plugins using content prepare. This can be enabled for Custom HTML fields under the Parameters tab or for any field under their Parameters > Layout parameters when using custom layouts. Joomla comes with a content plugin to load modules using the below usage.
docs.joomla.org/How_do_you_put_a_module_inside_an_article%3F
I assume by module slider you mean a Joomla module that provides that functionality or a Joomla content plugin that does. The above parameter usages should cover both cases.