Splitting the Fz into 2 accounts is standard practice. I am told it is explicitly permitted in the legislation (I am not a lawyer!). The tax authorities accept it.

Banks report dissolution of Fz and pension accounts directly to the pertinent tax offices and usually subtract the tax liability before paying out the after-tax amount. So there is nothing clandestine or evasive about the procedure.

Some Cantons (e.g. St.Gallen) are unhappy about this splitting, when the withdrawals are close to each other. Then they just club the 2 withdrawals and assess.

Hence, always split. Best case separate assessment. Worst case clubbing for assessment. Not an offense!