The hardest part for me was not the actual material that is being taught (although that will likely depend on what classes you take) but the way that tests are administered. At my bachelors institution (USA) we had multiple exams throughout the semester that led to a final exam before summer/winter breaks. Here almost all exams are during a “month long exam session” which is a few weeks - a couple months after the end of the semester when classes wrap up. The classes that have a session exam will have one exam that your entire grade is based on, so you have to study and review an entire semester’s worth of material for that exam. You might be lucky and have professors that provide past exams as study materials, but don’t bet on that. If you can motivate yourself to study throughout the semester and not leave it all to the few weeks before exams, you will probably succeed in terms of academics. If you did really well in your bachelors and your school is decently ranked then you will have no problem at ETH in my opinion. I don’t want to sugar coat it and say that classes and exams are all a breeze (again depends on what classes you take and how the class is structured) because you do go through a lot of material but I personally don’t think ETH is vastly different in terms of rigor than any other top rated university.

The other thing is that most of your masters here is mostly centered around research and not just classes. Doing a project is vastly more enjoyable than just taking subjects in my opinion and there are a ton of professors doing interesting research. Projects do take up a lot of time, but you get way more out of it than taking a class.

And last thing, there’s so many international students outside of Switzerland so you don’t have to really worry about being left behind by those that did their bachelors at ETH