Zig 0.15.1 got released over a month ago (git tag on 20th August, github release on 29th August). I searched in the bugzilla, the source repo and the mantainer’s copr and could not find any clue about why it has not yet been packaged.
In the past, for 0.14.0 for example, there was this pull request tracking the blockers and issues to be fixed before the package could be shipped.
Are there blockers to it at the moment?
Would it be possible to create a pull request like the one for 0.14.0 for tracking purposes?
From the repo, you can follow the link to the Zig issues and there you will find issue 2389355, which was created by the automated upstream release monitoring. It is already assigned to Jan Drögehoff and he left a comment, so he is definitely aware of the issue.
As for why it’s not been updated, it may simply be due to a lack of time, a lot of Fedora packagers are volunteers, who may have day jobs, families, other responsibilities, etc.