Hello! It's great to hear that you're planning a trip to Zürich, Innsbruck, Munich, and Salzburg. I can definitely provide some travel tips to help you prepare for your journey.

Best Time to Visit:
The best time to visit these European cities is during the spring (from April to June) or the autumn (from September to October) when the weather is pleasant and the cities aren't too crowded. However, if you wish to enjoy winter activities, then December to February is ideal especially for Innsbruck and Salzburg.

Route and Accessibility:
Starting your journey from Zürich, you can travel to Innsbruck using the European rail network which is efficient and scenic. From Innsbruck, you can catch a direct train to Munich. Similarly, Salzburg is easily reachable by rail from Munich.

Accommodation and Booking:
These cities offer a range of accommodations to fit different budgets. It's recommended to book in advance, especially during the peak season. Websites like Booking.com, Airbnb, or local hotel websites can provide a wealth of options.

Clothing and Essentials:
Clothing would largely depend on the time of your visit. However, comfortable walking shoes are a must. Packing a rainproof jacket is advisable as European weather can be unpredictable. Don't forget essentials like travel adaptors for European plugs, any prescribed medications, and sunscreen.

Health and Safety:
Standard health and safety precautions apply. Get travel insurance, keep emergency numbers handy, be mindful of pickpockets in crowded areas, and drink bottled water. Make sure you are up-to-date with routine vaccines before traveling.

Local Etiquette and Respect:
Europeans appreciate respect for their rules and social norms. Be punctual as it's considered a sign of respect. It's also expected to tip around 10% in restaurants. Dress appropriately when visiting religious sites. Try to learn a few words of the local language, as it's appreciated.