We had a lovely stay at the Zen apartment. It is located in 'The Pipe' area, walking distance from everything. Although you're in a central location, this street is pretty quiet and you'll only hear the occasional car or motorcycle drive by.
The place was actually even better than we expected. The hosts are wonderful and even offered toys and locations of nearby parks for our daughter. It was clean and had all the basic things you need (minus shampoo and conditioner, which we left for future guests ;) )
Previous guests had mentioned the construction across the street, and although seeing the site, we didn't see or hear any work happening during our stay. There was one instance where a terrifying sound woke us from our sleep but I think it was a garbage truck banging around as it didn't last longer than ten minutes.
Overall, we only have good things to say about our experience in Amsterdam. We definitely recommend this apartment!