I might not understand this correctly because I have never had the requirement to file such on my taxes, but a quick read says that need the maximum
value of the account in a given year.
Well here is a line from one of my Vanguard IRA accounts:

I can certainly guarantee that the value of my account is much larger then zero!
What is zero, and is true for the whole year is the "cash value". The securities value isn't being taken into account.