Change content of views_field_view field using hook_views_pre_render
Try using template_preprocess_views_view_fields

If you still can't access that field there then:


Ditch views_view_field
Add a "custom text field" (their field_name will be nothing).
In template_preprocess_views_view_fields programmatically add view to this "custom text field".


/sites/all/themes/THEMENAME/template.php

function THEMENAME_preprocess_views_view_fields(&amp;$vars) {
  $view = $vars['view'];
  foreach ($view-&gt;field as $id =&gt; $field) {
    if ($something == 'some condition') {
      $vars['fields']['nothing']-&gt;content = 'some string' . '&lt;br&gt;&lt;br&gt;' . 
        views_embed_view('view_name', 'view_machine_name', $contextual_filter_value);
    }
    else {
      $vars['fields']['nothing']-&gt;content = views_embed_view('view_name', 'view_machine_name', $contextual_filter_value);
    }
  }
}


If your view does not need a contextual filter, then it's:

views_embed_view('view_name', 'view_machine_name');