We've been fighting against those Curl errors for a while now (Dec 27, 2021) and it seems that those errors (namely 16 and 52) started bashfully but with time it grew stronger and stronger.
I use Tumbleweed, just like many people, and at almost every geeko # zypper ref or geeko # zypper dup I end up with headaches. When I see a new Tumbleweed Snapshot went out I know what's coming. Since we don't know yet what's really going on that's triggering those errors we have to cope with it until things are sorted out, and DNF might be the solution for now.
For those wondering, the Curl error (16) is not particular to Zypper, even DNF will run into it (or bare curl commands if you're patient enough). Another thing we know is that if a package fails to be retrieved, trying again will solve the issue because it happens in a sporadic manner, maybe it will take a couple tries, maybe several, but the package will be d