German is the official written language in Zurich, but Swiss German (Schweizerdeutsch) is spoken in daily life and sounds quite different. High German (Hochdeutsch) is always understood and will get you everywhere.
Where to start
Most expats start with standard High German courses — either private school (Migros Kulturprogramm, Sprachschule Zürich, Berlitz) or apps (Duolingo, Babbel). High German is taught in schools and universally understood.
Swiss German
Swiss German is a collection of dialects — Züridütsch in Zurich, Bärndütsch in Bern. There are private classes (e.g. Schwizerdütschi Spraachkurse) but most expats pick it up informally over time. Understanding Swiss German takes 6–12 months of immersion.
Language requirements for permits
A C permit (permanent settlement) requires proof of language skills: B1 level (written) and A2 level (oral) for German, French, or Italian. Swiss citizenship requires C1 level.