Olena_fromHK Hi,
The trains between Domodossola - Brig - Zermatt are running, only the EC between Milano and Domodossola are canceled.
You can buy the tickets from Milano to Zermatt now on trenitalia.com, but the same tickets should be also available on sbb.ch in the next days. On sbb.ch you can buy Supersaver Tickets or Saver Day Passes who are not available in Italy. It is better to wait or buy only the bus ticket on trenitalia.com from Milan to Domodossola and the train ticket on sbb.ch from Domodossola to Zermatt.
Supersaver Tickets and Saver Day Passes are not refundable and not exchangeable. Point-to-point tickets are refundable until the day before departure. With Supersaver Tickets you must use the train you selected.