I'm looking for an upcoming trip that has me transiting in Frankfurt via Lufthansa onwards to France - it's not a major city hence the need for a transit.
The thing is, the proposed layover is 1h 45min. I would like to know if this is enough, seeing that since I'm not from the EU, I have to clear passport control in Frankfurt before going for the connection. Or would it be better for a slightly longer one of 3 hours at Zurich airport (via Swiss Air)?
You haven't told us where your flight originates. If you're from the USA, remember that most of the world is not the USA.
Frankfurt is a very efficient airport indeed, so you'd probably just about do it IF your baggage has been checked through to your final destination, but whether that's likely to be done is something you would have to ascertain from Lufthansa.
Personally, I would not be satisfied with less than 2 hours between flights -- you've got to allow for potential delay in the arrival of your incoming flight and queues at security.
I've no experience of Zurich airport, though the Swiss are normally hyper-efficient. 3 hours is a much more comfortable gap between flights since security checks seem to have been intesified everywhere over the past year or so..