When you asking for your tax back (considering you got taxed to the source every month) for the 3rd pillar account, you must do it EVERY year, before March 31st.
I just contacted "Zürich Cantonal Tax Office"
: you CANNOT get the tax (money) back from a previous year past this date.
For example: in March 2015 you can claim your taxes back for the year 2014, but not for 2013, nor 2012 nor any previous year - and from April 2015, you cannot claim anymore for 2014.
My final advice on this topic: EnglishForum is great, you will get tones of good tips, but you should always double check the information provided as I have read a lot of false information on this very website too.
In this case, you can contact (phone, email or face-to-face):