Sync Outlook 2013 with iTunes 12.5.1
In case you don't want to use iCloud, you can try 3-rd party software called AkrutoSync. Unfortunately, there's no way for syncing over USB, only via Wi-Fi or over the Internet. The best part is that this software works with iPhone's native apps which I found very convenient. Here's a link to their website: http://www.akruto.com/sync-iphone-with-outlook/

The bad thing is that you have to reconfigure this software each time you want to switch between syncing over the Internet to syncing via Wi-Fi.