Cash allowance while transiting through Zurich

This page, from the Swiss Customs authorities, says that currency does not need to be declared, but that there are checks if you have more than CHF 10,000:

Unrestricted amounts of liquid funds, i.e. cash, foreign currency and securities (shares, bonds and cheques) can be imported into Switzerland, brought through Switzerland in transit or exported from Switzerland. Furthermore, the funds do not need to be declared.

Checks on the cross-border movement of liquid funds

To combat money laundering and terrorist financing, we can carry out checks. If you are carrying CHF 10,000 or more, we will question you. In doing so, you will have to answer questions concerning you and the origin and intended purpose of the money, and provide information on the beneficial owner.

Consequences of the checks

In the case of liquid funds of CHF 10,000 or more, an entry will be made in the information system of the Customs Administration. If there is a suspicion of money laundering or terrorist financing, the funds may be temporarily confiscated or handed over to the police. The right is reserved to take other measures linked to combating crime.

Legal situation in the European Union

Liquid funds of EUR 10,000 or more must be declared in writing to the respective customs authorities when entering, passing through and leaving the European Union and its member states.

Given the importance of doing this right and the danger of having your currency seized, by Switzerland or the US authorities, I would encourage you to seek legal advice instead of relying on strangers on the internet, or better yet, simply not do this at all. In the case of the US, traveling with slightly less than $10K could be risky, because the authorities might believe you are intentionally carrying just under the amount that must be declared to evade the reporting requirement, which makes you look quite suspicious.

I recognize that Tajikistan has currency controls that may pose an obstacle, but bank transfers are usually a better option for lawful transactions, due to the greatly reduced risk of loss, theft, or official seizure.