According to the Wiki documentation, building with zlib-ng requires specifying ZLIB_REPOSITORY and ZLIB_TAG with CMake. This does not seem to be working for me (tested on Windows with CMake 3.21.21080301-MSVC_2).

Instead the variables that need to be defined are zlib_REPOSITORY and zlib_TAG, because the "zlib" parameter passed to clone_repo, which is used to create these variable names, is lowercase:

With this the library is fetched correctly. This should be fixed either in CMakeLists.txt or the Wiki.

-- Fetching zlib https://github.com/zlib-ng/zlib-ng 2.0.6
-- Using CMake version 3.21.21080301-MSVC_2
-- ZLIB_HEADER_VERSION: 1.2.11
-- ZLIBNG_HEADER_VERSION: 2.0.6

However, even when passing these arguments I’m getting the following error:

-- The following OPTIONAL packages have not been found:

 * ZLIB

-- Using CryptoAPI
CMake Error at CMakeLists.txt:733 (install):
  install TARGETS given target "zlibstatic" which is an alias.