The most efficient way is to use an open source explorer used to handle/manage Azure storage: http://azurestorageexplorer.codeplex.com/
It handles multiple credentials smoothly without any conflicts, and also lets you perform several managerial operations(copy, rename, delete, and download) withou hassle.
So, once you have downloaded the .vhd file from any account on to the local machine, try uploading the file using the below simple command:
azure vm disk upload
- on PowerShell.