I don't have one particular favourite to be honest. There's a bunch that I like:
Maybe it's just for the memories, but I still enjoy listening to this game's music from time to time. Some of my favourite tracks are the Water Temple, the Spirit Temple and Zora's Domain's music.
This whole series has a great soundtrack, but in the end I found myself liking Skyrim's the most. Especially the more ambient music you hear as you traverse the mountains or explore towns is lovely and relaxing in my opinion. It goes very well with all the sounds of nature you can hear (wind through the trees, waterfalls, etc.).
I loved the soundtrack for having lots of references to music I like (e.g.: The Beatles, The Doors, The Who, Pink Floyd).
Can't come up with anything else right now...