I got two questions.

Note: Assume I got a current domain name that needs to switch name servers without any downtime. I got two general questions:

1# Can I sign up for something like xnames or zoneedit, setup my DNS records, wait a few days till it propagates throughout the internet, then go to my DNS and switch name servers to xname/zoneedit, so I get 0 seconds of down time? Or will it somehow cause it not to propagate throughout the internet without also switching my name server?

2# Can I sign up for both xname and zoneedit, both set them up the same way, then setup the domain with both of them as nameservers? Would this somehow break anything using two completely different name servers? Seems to me this (free) setup would help insure the site doesn't go down if either zoneedit or xname go down.