Two different Apple IDs with two different @icloud.com mails
No - if you really have two different AppleID each with different @icloud/@me/@mac addressed - they cannot be merged or swapped one for the other. If you just want to use the @icloud.com to log in to one AppleID that's also known by a different email address - you can do that easily by changing the username on each device.

See Apple ID - Want to make my xxx@icloud.com primary Apple ID?

If you have two AppleID - the best you can to towards merging them might be to make a family plan and share purchases and migrate mail/contact/calendar data off the account you wish to avoid.

See Renaming iCloud mail address for that.