A Zippo would not be my first choice for SHTF deal. Things are heavy maintenance and heavy compared to small disposables. They dry out
I'd just buy a small crate of BICs. That and a good knowledge of how to make friction fires and just call it good.
They can last incredibly long if you are not a smoker. I have always valued portable fire, so I always carry a mini BIC in my pocket. If I don't lose it, I buy a mini once a year. Still might be OK, but I chunk them after 12 months and get a new one. I have a full size BIC I bought to leave in my tool box at work. I burn rope ends or light the occasional torch with it. It is 14 years old. It was an older one I retired from my get out of Dodge bag. Best guess is the thing is at least 15 years old and it still sounds like it's half full of fuel.
If things did not eventually take an upswing after a SHTF crash, I doubt I'll even survive a dozen BICs, even if I use them every day to light cook fires.