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

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

[ebuild   R    ] sys-libs/zlib-1.3.2-r1:0/1::gentoo  USE="minizip* -static-libs -verify-sig" 1290 KiB
[ebuild  N     ] virtual/minizip-1.3.1:0/1::gentoo  USE="-static-libs" 0 KiB
[ebuild  N     ] media-libs/assimp-6.0.2:0/6::gentoo  USE="-collada -doc -samples -test" 148658 KiB

Total: 3 packages (2 new, 1 reinstall), Size of downloads: 149947 KiB

The following USE changes are necessary to proceed:
 (see "package.use" in the portage(5) man page for more details)
# required by virtual/minizip-1.3.1::gentoo[-static-libs]
# required by media-libs/assimp-6.0.2::gentoo
# required by =media-libs/assimp-6.0.2 (argument)
>=sys-libs/zlib-1.3.2-r1 minizip