Could NOT find ZLIB

I have tried running emsdk on Windows 11, wsl on Windows, and also on a Debian VM. I get the same behavior in all 3 with the latest emsdk. I am trying to build a project that supposedly already has emscripten support. I tried adding a use flag for zlib, but it cannot be found. I have the dev packages installed in Linux and can compile natively for Linux, but not with emsdk for emscripten.

What I'm trying to compile is:

https://github.com/gerstrong/Commander-Genius

if( ${CMAKE_SYSTEM_NAME} MATCHES "Emscripten")
set(USE_FLAGS "-sUSE_SDL=2 -sUSE_SDL_IMAGE=2 -sUSE_SDL_TTF=2 -sUSE_SDL_MIXER=2 -sUSE_ZLIB=1 --use-port=zlib -sUSE_OPENSSL=1 -sUSE_CURL=1")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${USE_FLAGS}")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${USE_FLAGS}")
set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${USE_FLAGS}")
set(CMAKE_EXECUTABLE_SUFFIX .html)
else()
find_package(SDL2 REQUIRED)
find_package(SDL2_IMAGE REQUIRED)
find_package(SDL2_TTF REQUIRED)
find_package(SDL2_MIXER REQUIRED)
find_package(ZLIB REQUIRED)
find_package(OpenSSL REQUIRED)
target_link_libraries(untitled OpenSSL::SSL)
find_package(CURL REQUIRED)
endif()
include_directories(
${EMSCRIPTEN_ROOT_PATH}/system
${CMAKE_SOURCE_DIR}/include
${SDL2_INCLUDE_DIRS}
${ZLIB_INCLUDE_DIRS}
${OPENSSL_INCLUDE_DIRS}
${CURL_INCLUDE_DIRS}
)

**Version of emscripten/emsdk:**
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.55 (165133b1cc977f0b9a277e42ef809b823157189c)
clang version 19.0.0git (https:/github.com/llvm/llvm-project 6c7805d5d186a6d1263f90b8033ad85e2d2633d7)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /root/emsdk/upstream/bin

**Failing command line in full:**
emcmake cmake ..
configure: cmake .. -DCMAKE_TOOLCHAIN_FILE=/root/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -DCMAKE_CROSSCOMPILING_EMULATOR=/root/emsdk/node/16.20.0_64bit/bin/node
-- Found Git (/usr/bin/git), executable will get SHA and branch used
-- GIT_SHA = 1645a70e8
-- GIT_BRANCH = master
-- Setting SYSTEM_DATA_DIR to /usr/share/games
-- Setting build type to 'Release' as none was specified.
-- Preparing the Build-System for Commander Genius
-- Internal Downloader: ON
-- Keen engine build enabled
-- Refkeen engine build enabled
-- Found PkgConfig: /usr/bin/pkg-config (found version "1.8.1")
CMake Error at /usr/share/cmake-3.28/Modules/FindPackageHandleStandardArgs.cmake:230 (message):
Could NOT find ZLIB (missing: ZLIB_LIBRARY ZLIB_INCLUDE_DIR)
Call Stack (most recent call first):
/usr/share/cmake-3.28/Modules/FindPackageHandleStandardArgs.cmake:600 (_FPHSA_FAILURE_MESSAGE)
/usr/share/cmake-3.28/Modules/FindZLIB.cmake:199 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
src/engine/unzip/CMakeLists.txt:16 (find_package)