Sorry if this answer has already an accepted answer, but unfortunately it needs a major clarification
Is there any site where I can find full details of the platform numbers in advance
Generally not, and depends on how in advance. Train platforms are similar but not identical in concept and management to airport gates. It's a lot less bulky for a train company to get a platform at a station than an airline to get a gate (and all required staff) for a flight.
This because tracks are assigned really shortly to train's arrival at the station, for a variety of reasons. Railway traffic control has a few constraints over the choice of the track/platform to assign to a train:
- Electrification: a train not running a HSL (25000V AC) must be routed to a regular line (3000V DC)
- Length of the train: a fully-featured two-stock ICE can't enter a half-track in a terminal station, which is used for regional traffic
- Availability of outbound track: in my experience, this often results in long-running trains stopping at the middle in the middle of a large station (e.g. it comes from the line on "your left" and will proceed to "your right", to simplify a lot)
Indeed, if you connect to SBB's real time traffic, you can get realtime data
And no, you can't know long before departure, unlike airport gates.
to avoid getting lost at the station
Getting lost at Zurich HB is a hard work. Once you get off the train, find your numbered platform, head to the head of the platform and look for the timetable, which will likely indicate your next platform given the short layover.
Kudos to @jcaron's comment, reported verbatim
Most internal trains in Switzerland won’t wait for delayed passengers as the regular scheduling usually means you can get another train within the hour, sometimes much less. However the last train of the day on a given route is usually an exception. Make sure you advise the train master of your connection if your train runs late