Thalwil is on my commute home (ish....I'm Zurich <-> Unterageri). It's biking only for me, and I'm 8kg over race weight, so my fitness is very VERY poor.
However, more than welcome to join you as my fitness improves.
Warning: as a former trackie, my forte is normally sprinting and flat power not climbing; something I will need to adapti suspect, now I'm in CH.