ReadyNAS 104 RAID5: 'Remove inactive volumes' after crash during resync - recovery needed

You were smart not to experiment.  Have you tested the failed drives with vendor tools to see if they are accessible at all?

What happened to you is exactly why you need to make a full backup before replacing a drive and really should keep a backup current daily.  You do not have three consistent drives because a second drive failed before the other failed drive's replacement completed re-sync.  Especially if all the drives are the same age, that's the case all too often because a re-sync puts extra strain on the drives.  If either of the failed drives work well enough to clone it, you may be able to recover at least some of the files.  If not, your chances are poor.  I'm sure StephenB​ will offer to look at your logs, but you can't upload zip files here.  So put it in DropBox, Google Drive, etc. and prepare to share the URL in a PM when he asks for it.

data and data-0 are two parts of your RAID that the OS cannot put together, so do not attempt to delete or do anything to either.  Doing so will reduce your chances of recovery even more.

The 7/11 and 7/25 re-syncs ending as "degraded" means you already had one bad drive at that time.