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"Do taxis accept non cash payment in Zurich?"
Yes, you can pay by Visa, Mastercard, Maestro, Amex and Diners. See HERE
"Is there any alternative transportations from Airport to Stadion Letzigrund?"
Yes, take the S16 suburban train from the airport to HardbrΓΌcke (7-8 minutes), from where it's a 1-km walk.