Hello, good day and thanks for your question. I understand that you are looking into resetting the solitaire statistics and cloud to zero.
As there is already a record of a login and if there is also a progress on the account, a reset specifically on the cloud might not be possible but you can check this with the Microsoft Casual Game support if this can be done and this will determine whether this is possible once they have responded to your query at submit a request.
You can logout and login with a different account locally on your PC but the cloud part is the ones that is different.