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

Calculating dependencies ... done!
Dependency resolution took 1.02 s (backtrack: 0/20).

[ebuild  N     ] net-libs/zeromq-4.3.5-r1:0/5::gentoo  USE="libbsd sodium -doc -drafts -static-libs -test -unwind" 2471 KiB
[ebuild  N     ] net-libs/cppzmq-4.10.0::gentoo  USE="-test" 46 KiB

Total: 2 packages (2 new), Size of downloads: 2517 KiB