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

Calculating dependencies ... done!
Dependency resolution took 1.56 s (backtrack: 0/20).

[ebuild     U  ] app-shells/zsh-5.9.1::gentoo [5.9.0.3-r2::gentoo] USE="gdbm pcre -caps -debug -doc -examples -maildir -static -valgrind -verify-sig%" 3335 KiB

Total: 1 package (1 upgrade), Size of downloads: 3335 KiB