Essentially every bank that supports Zelle has in their terms of service:

The following types of payments are prohibited through the Zelle® and Other Payment Services, and we have the right but not the obligation to monitor for, block, cancel and/or reverse such payments:

F. Payments relating to transactions that:

e. are associated with the following “money service business” activities: the sale of traveler's checks or money orders, currency dealers or exchanges (including digital currencies such as Bitcoin), or check cashing; or

https://banking.fnb-onlinebankingcenter.com/FNBPA/Enrollment/ConvertedUser.aspx