In order to transfer VHD from one storage account to another, you don't need to do that. In fact, I will go out on a limb and say "Please Stop Using Azure Storage Explorer". This tool has not been updated in ages and does not have the latest functionality offered by Azure Storage.
Azure Storage supports Async Server Side copy blob which will copy the blobs from one storage account to another on the server side without having to download the blob first from source storage account and reupload it in target storage account.
I would recommend using AzCopy
which is now part of Azure SDK. If you've the latest version of SDK installed on your computer, you can find it in C:\Program Files (x86)\Microsoft SDKs\Windows Azure\AzCopy
folder. Here's the sample usage to copy file from one storage account to another:
AzCopy "https://<oldaccountname>.blob.core.windows.net/<oldaccountcontainername .. usually vhds>/" "https://<newaccountname>.blob.core.windows.net/<newaccountcontainername .. again vhds>/" "<filenametocopy.extension" /SourceKey:<oldaccountkey> /DestKey:<newaccountkey> /BlobType:page /S