Hi @molnfront, we have a couple of threads going on so I want to make sure everything is clear, I apologize if some of this is redundant:
Goal - move trommeteambuilding.dk from one Cloudflare account to a new Cloudflare account.
Blocker - The name servers are responsive from the old account and set to:
$ dig ns trommeteambuilding.dk +short
as a result, the registrar DK is unable to change the name servers.
Action - From the old account (the one with Pat & Lee servers), delete the zone and ask support to purge it per this information, https://support.cloudflare.com/hc/en-us/articles/204615358-How-to-move-domains-between-Cloudflare-accounts
Steps After Above Action - Once the zone is purged from the old account, ask DK to revert your name servers to their original settings, verify they are responsive, add the zone to Cloudflare and note the new nameservers assigned to your account, give those names to DK and ask them to update from the original name servers to the new ones.
The above all assumes you are unable to access the existing account and that after delete & purge DK can successfully change the name servers.