Writing zeros is good for the average person that does not have skills to recover your data. If you are more concerned, use "boot and Nuke" which allows many methods to securely write over your data. I believe it is free also.
For drives other than my personal computer (HTPC and such), I just write zeros to the drive since there is noting needing security. If it is my personal drive with my data on it, I use boot & nuke.