Yes, when coming from Germany you can just walk out. As long as there are no flight delays, you should be able to meet your friend very close to the scheduled landing time.

When departing to the US, you do need to go through passport control after security. Also your flight will likely depart from E gates which means getting a train, and occasionally there is extra profiling at the gate itself. I don't think ZRH is experiencing problems to the scale seen in other European airports, so even as late as 45 minutes you may have a chance of making it, but I would probably head off at around 75 minutes before scheduled departure.

Also you can observe the security queues on the way out and if they seem quite busy you may want to allow more time. And if you are a non-EU/EEA/Swiss citizen, while they don't tend to ask any questions on departure so everyone gets through relatively quickly, the passport control queue may also be longer.