Is there anyway to unmerge and restore my database collection back to previous state
What exactly did you merge? Did you merg albums into a multidisc album? This can not be undone.
Or did you merge collections into 1 collection?
If everything is always in sync with CLZ Cloud (did you regularly sync?), we may be able to restore a backup for you. Please share more details on what happened on your side so we can hopefully help you out.