I'm not sure there is any kind of exceptional software engineering cluster in Zurich compared to other major European cities. But even if there were, it wouldn

I'm not sure there is any kind of exceptional software engineering cluster in Zurich compared to other major European cities. But even if there were, it wouldn't matter to Google. There are no major network effects or cross-pollination with the ecosystem. Practically everyone who goes to work at that office is relocating from elsewhere. And if people leave, it's rarely to work at some other company in Zurich, but usually to move to another country. I'm not saying that ETHZ and EPFL aren't great universities. I just don't see any reason to believe they are a major factor in this particular case, directly or indirectly. (Just to give an idea of where my comments are coming from, I worked at Google Zurich for 4 years, and then another 4 doing a Zurich-based startup).