Changing trains in Switzerland is not a challenge. Once arrived at Zürich HB, platform 32 you simply follow the signs to platforms 3-18. Although doable, the transfer time is rather tight. If your ticket allows it, take an earlier train to have at least 30 minutes to change in Zürich; it would mean a pity if you miss the TGV just because IC1 was unexpectedly late.
There is no custom and passport procedure before boarding the train; all will happen on the train.
Wishing you good travel.
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