These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.05 s (backtrack: 0/20).

[ebuild  N     ] dev-util/vulkan-headers-1.4.363.0::gentoo  USE="-test" 3337 KiB
[ebuild  N     ] dev-util/vulkan-utility-libraries-1.4.363.0::gentoo  USE="-test" 1316 KiB

Total: 2 packages (2 new), Size of downloads: 4652 KiB