The official TSA allowed/banned list is here (PDFfile). The filename changes as the list is updated, so perhaps it's wiser to go here and click on "Permitted and Prohibited Items".

the current answer is:
Safety Razors: Permitted in carry-on and checked baggage.
Matches/lighters: "Up to 2 lighters or 4 books of safety matches are allowed in your carry-on baggage - NOT checked baggage. Disposable lighters and absorbed liquid lighters are allowed in your carry-on baggage. Lighters with unabsorbed liquid fuel are NOT permitted. Strike anywhere matches are NOT permitted."

I think a Zippo is an "absorbed liquid lighter", isn't it?

EDIT: I'm not sure, but I think that for international flights the rules of the country of origin apply - my rational being that in many/most international airports the flights aren't segregated by destination country (or in some cases even by domestic vs. international destination) so a single set of criteria need to be applied at the security checkpoint. So while these are probably the rules for the SFO-CDG leg, the return rules might be more restrictive.