Your site is currently doing what is called a conditional redirect with the condition being that the referring page is a search engine. When a request is made for a page on your site the request provides your server with some additional information beyond which page is being requested. The information provided varies but typically the request will include information about the user agent, ie the browser being used to make the request, and the referring page, the page that contains the link that is being clicked on such as a search results page.  These types of conditional hacks are frequently used by hackers because it normally takes longer for site owners to discover and remove the hack.

For sites hosted on Apache one of the most common ways this type of hack is accomplished is a hack of an Apache file named .htaccess.  This file is typically located in the root directory of a site although there can be multiple .htaccess files on a site in multiple directories. On some sites .htaccess files may be located in directories/folders above the root directory of the site.

  
Check the .htaccess file for any suspicious redirects, redirects to   http:// hinia . zyns.com/  be sure to scroll all the way to the bottom of the file hackers sometimes add 100s of blank lines before the malicious code,  "tab the code way over, and then add 100s more blank lines.