If we're in the kind of crisis where all fiat money is useless, gold will be useless too. The only kind of thing that will have value are things that help you survive. A crate full of gauze pads and bandaids would be better than a whole stack of gold bullion in that situation.
There is quite a continuum between fiat currency collapsing and the sort of zombie apocalypse you describe.
Fiat currency has become worthless many times in many countries without a total breakdown of civilization to the extent that gold no longer has any value (e.g., Argentina, Yugoslavia, Brazil, Weimar Germany, post-revolution France, ...)
In a country scale crisis people would be selling all their valuables for fire sale prices to pay for essentials, including gold. A fiat reserve currency, like the Swiss Franc or the Pound would be easier to use, less likely to be stolen and more valuable then gold shavings.
Gold isn't going to save you from a zombie apocalypse, nor can you eat it.
It will however transport your wealth from one side of a currency crisis to the other while retaining value - as opposed to plastic notes with arbitrary numbers of zeros printed on them.
