Bixoazie87
Which connection / schedule did you look up exactly?
The typical PE / IR70 connection (Interlaken - Meiringen - Luzern - Zurich) suggested by the online timetables allow 14 minutes transfer time in Luzern.
Also in my opinion, even 5 minutes should be sufficient if the incoming train is not delayed. (The distance between the involved platforms is not THAT relevant, maybe a minute or so. The point is the length of the trains / where “your” carriages are located, however you could also walk inside the trains while they’re moving)