Time enough in Frankfurt after Zurich flight?

Yes.

There will be train connections to Frankfurt the day before. Most trips take just 4 hours. 15:59 - 19:52, for example. Sleep there near the main station, get to the airport on the local train (10-12 minutes) whenever your airline wants you there - very likely before 6 am that morning.

Is Zurich-Frankfurt-Dallas one ticket? If it is one ticket it is tight but the airline sees it as feasible. If it is one ticket and you take the train (skipping the Zuriich-Frankfurt segment ) the airline will have cancelled your flight to Dallas

If you have separate tickets, you are in grave danger

My response assumed separate tickets.

If it's all on one ticket, which I doubt, then your airline should handle the rescheduling of your 2nd flight should the first one be excessively delayed.

When people post questions like this, it's unfair. You don't tell us the date, or the flight numbers, or the airlines, or all the other information that would allow us to go on, for instance, the Frankfurt airport website and see the gates used for the flights. Are they all in the A/Z concourse, where only a change of floors (and outgoing emigration passport check) is required, or does does one flight come into Terminal 2 (Concourses D/E) and the other flight leave from T1, Concourse Z and require time using the SkyLine, security, etc?

Please give us more information.

If you arrive in the A concourse and depart from Z, I think you can make it in 55 minutes.

I am pretty sure it is on one ticket. And if the flights are on time it should not be an issue. There is no need to re clear security, and exit passport control is usually fast. Just follow the signs.

If have had connections that tight in FRA where I still had time to visit the lounge.

The important thing to remember is that the airline wants this to work. They have every incentive to make this work. And they know when your plane from Zurich landed, at which gate you deplaned, and how far the walk is from there to your next gate. So they have a pretty good idea when they can expect you to turn up for the next flight. Within reason they will even hold the flight to Dallas.

More details:
It's all one ticket

Dallas-Zurich Flight LH 439
Arrive Frankfurt 8:15 Terminal 1
Dep for Zurich 9:45 Terminal 1, LH1186

Zurich -Dallas LH 1183
arr Frankfurt 9:15 at Terminal 1
Dep for Dallas 10:10 LH 438 in Terminal 1

Thanks all for good advice

Update: In Frankfurt airport today 7/2, Zurich flight on time, Dallas flight on time, BUT chaos in the airport at security! Line for Z gates extended through multiple hallways of Terminal 1. We missed our Dallas flight, as predicted....now waiting in line for Lufthansa to rebook, but not optimistic on that either...at least we aren't in Texas heat yet.

I am a bit puzzled. You should not have needed to re-clear security arriving from ZRH. Only passport control. Did you take a wrong turn and end up land-side by accident? Has happened to me too.

Hope you got home alright.

Fingers crossed!

For the future reference of others, I am just reacting on the earlier suggestion to stay near Frankfurt main station the night before. That's not ideal, because the station neighborhood is really not the best (significant drug issues). Best to stay by the airport, or in the center of Frankfurt (S-Bahn takes you to the airport anyway).

@wengen we along with hundreds of others headed to US had to go throughout passport control, we weren't on the domestic side.

We were rebooked on a flight through DC which also didn't allow enough time, so were told the gate was closed. About that time the pilots arrived late and we got onboard. Lufthansa just does not allow enough time to transfer.

Ugh, I also have a 55 minute layover in Frankfurt for our trip home from Geneva in a few weeks. ( I accidentally booked it, I had multiple screens open, booking several different tickets at once). :/

ETA: CORRECTION - layover in Munich, not Frankfurt. I don't know if that's better or worse.

Munich is definitely better. LH build its terminal there with the express aim to make short transfers possible. The MCT there is 30 minutes.

You will pass through security in ZRH (but not passport control, as this is still Schengen internal), which last time I was there (Wednesday a week ago) took me 12 minutes.

In Munich you will go through passport control as you are leaving the Schengen common travel area there, but you won't need to go through security again.