Backing up to two external drives

Hello,

I need to backup 20TB of data.    The client is too cheap to do anything but TWO 12TB external drives.   THey want to use Windows Server native backup.

How do I back up some VMs to one drive and some VMs to another.

Please don't explain how important backups are and how they should consider another alternative.  I have to implement what they want.   I'm familiar with VEAM, disk arrays, replication servers, cloud backup, etc.   There is ZERO money in the budget for anything else.  They already have the two external drives.