I've transferred a domain to Godaddy, keeping the custom nameservers, as I didn't want to change anything.

I'll probably need to edit A and CNAME records soon but I can't, as it says "The zone file is unavailable because the domain's set nameservers do not belong to this registrar.".

So, I need to set the nameservers to Standard "Go Daddy hosting, forwarding, and parked domains." before I can edit these settings. 

If I change the nameservers in GoDaddy and immediately after edit the zone to match the current records (A and CNAME), will there be any downtime? I've contacted them but had different answers.