I have Google Analytics (Asynchronous) script

    <script type=”text/javascript”>    
    _gaq.push(['_setAccount', 'UA-XXXXX-X']);
    _gaq.push(['_trackPageview']);    
    (function() {    
    var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;    
ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';    
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);    
})();    
</script>

and Google Analytics with Display Advertising Script

<script type="text/javascript">
var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'UA-XXXXX-X-yz']);
_gaq.push(['_trackPageview']);    
(function() {
var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
ga.src = ('https:' == document.location.protocol ? 'https://' : 'http://') + 'stats.g.doubleclick.net/dc.js';
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
})();
</script>

The UA - codes are different can i use both the codes ?

I've read some where that Universal Analytics will not interfere with previous versions of Google Analytics.

If i have upgraded to Universal Analytics, If the UA - codes are different should i use only the Universal Analytics script or should i use both Universal Analytics script and Universal Analytics script.

please advise.....