Leaving Outbound Flight on 1st Stop?

Yes. Your return flight will probably be cancelled and you risk being charged the real-time fare difference plus steep penalty. They already have your credit card info.

There's a good chance your return flight may be canceled. As to further retaliation, you may (can probably) get away with doing this once or a couple times. If you make a habit of it, airlines have banned people for doing this. They take a very dim view of it. Some people do it and live to tell about it.

You may be able to get away with it on a return trip or leg but not on your outbound. I have never heard of it working on an out bound leg. Your risk is very high. If you do it going and your return is cancelled what do you do? Buy an expensive one way return home. You are assuming a lot of risk if you try it outbound. It is also a security issue that the airline does not take lightly. If you go missing, what did you leave behind.

Odds are not with you on this. It might work if the airlines were not in the same alliance but your return ticket will be canceled. This is a type of hidden city ticketing. Lufthansa sued someone about this and though they lost, they appealed -- not sure what happened with the appeal. You might want to read this article: https://www.travelandleisure.com/travel-tips/hidden-city-ticketing-consequences The airline will absolutely cancel your Paris to SFO flight. That I can guarantee because they will know you made it to Zurich and they will also know that you skipped the Zurich to Paris flight. Every subsequent leg on that itinerary will be canceled with no refund. Even sites that encourage hidden city ticketing tell people to do it only for the last leg of a trip.

Two one way flight will cost an arm and a leg. Just look for one stop flights.

Use Google Flights, set a filter for one stop flights, and see what comes up. SFO-ZRH-SFO

Whether two one-way flights would be expensive depends entirely on the airlines that fly between cities. I've seen plenty of cheap one-way fares from the US to Europe. Definitely worth checking the options and not making assumptions.

Whether two one-way flights would be expensive depends entirely on the airlines that fly between cities.

That's true, but the case cited by the OP is a perfect example of an airline that is looking to maximize profit by making the customer choose between paying more for getting what they want (a direct flight to Zurich), or getting a lower price by accepting an inconvenient/unwanted and longer routing. This is at the core of most major (legacy) airlines' pricing algorithms.

The airlines know what you want (a nonstop flight, or one that minimizes stopovers, and all at a reasonable/convenient hour). They "monetize" that by forcing you to pay more (often a lot more) - even if it's a shorter flight that they already are running a segment of an itinerary that they'll offer at a lower price - for lower prices they offer flights that you don't really want. You want to go A to B, but they charge you more for that; they give you a "cheaper" flight from A to B to C.

This is not some quirk of the system, it's 100% intentional. They know what you want and just price it higher because, well, some folks will pay more. That's why "hidden city ticketing" is so tempting. It appears they are working hard to stick it to consumers (because they are). But that's how they make money, by charging you more for what you actually want, even if it costs them less than forcing you to take a roundabout routing that you don't want.

It seems crazy that they charge you more to fly a shorter, more direct flight, and they charge you less to fly extra legs that you don't want (and are tempted to throw away). But that's how they maximize profits.

Have you tried searching for a multi-city flight?

Google Flights is showing a Swissair SFO-ZRH nonstop combo with United CDG-SFO nonstop using some dates I chose in March for about $1300 to $1430 depending on class.

Your fares could be higher or lower depending on exactly when you're traveling.

If you are only going to Zurich and then going home, you can beat those $1600+ prices by having a stop along the way.

Or maybe by a RT SFO-AMSterdam plus a carefully scheduled RT AMS-ZHR on a European airline.

Good thing you asked the question. Don’t walk away from any flight segment because the rest of the ticket will be canceled. You would have found out when you tried to check in to fly back to SFO.

No, they probably won't charge you for doing this once.

But the bigger problem is "skyscanner" https://www.sitejabber.com/reviews/skyscanner.net

Skyscanner isn't selling you a ticket they are referring you to any number of sites which includes some horrid places like Kiwi!

If it's not an airline site or a well known travel site (Expedia for example) RUN!!! The reason Skyscanner is giving you this great deal is it's likely to have huge problems.

I'd suggest tracking your flight on Google Flights. Set up the alerts for a few different dates. You may find that prices change daily, or hourly. We found a great price on a direct SFO-Zurich flight last Nov, [granted off-season.] And - it was open jar, as we returned directly from Frankfurt. I have noticed that direct flights are cheaper 4-6 months out, as obviously they are more desirable, and probably fill up faster. Hopefully you have the time to monitor flight prices.
Many folks here report really low air fares to Paris, but be aware of the French labor strikes. I'm speculating that these lower air fares could be a result of folks avoiding French flights, after the December labor strikes? Search here for info on the ongoing labor union strike situation in France.
Safe travels!

You need to use a flight search engine, like kayak or google flights. Maybe flying through Amsterdam or Frankfurt is cheaper. Who know? I’ll tell you who knows - the flight search engines. Just plugin SFO to ZRH and see what is best.