Unbundle the zstr library (under the assumption that zlib support will
be unconditionally disabled) by removing it from some CMake lists.

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1dc3a98..05a0a6e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -820,7 +820,6 @@ if(NOT FAST_BUILD)
     ${HIGHS_BINARY_DIR}
     ${PROJECT_SOURCE_DIR}/app
     ${PROJECT_SOURCE_DIR}/extern
-    ${PROJECT_SOURCE_DIR}/extern/zstr
     ${PROJECT_SOURCE_DIR}/highs
     ${PROJECT_SOURCE_DIR}/highs/io
     ${PROJECT_SOURCE_DIR}/highs/pdlp/cupdlp
diff --git a/cmake/sources-python.cmake b/cmake/sources-python.cmake
index e5039bf..4dc7be4 100644
--- a/cmake/sources-python.cmake
+++ b/cmake/sources-python.cmake
@@ -1,6 +1,5 @@
 set(include_dirs_python
     $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/extern>
-    $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/extern/zstr>
     $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/highs>
     $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/highs/interfaces>
     $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/highs/io>
diff --git a/cmake/sources.cmake b/cmake/sources.cmake
index 983833a..31e0630 100644
--- a/cmake/sources.cmake
+++ b/cmake/sources.cmake
@@ -1,6 +1,5 @@
 set(include_dirs
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/extern>
-  $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/extern/zstr>
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/highs>
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/highs/interfaces>
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/highs/io>
@@ -446,8 +445,6 @@ set(highs_sources
 
 # add catch header?
 set(highs_headers
-    ../extern/zstr/strict_fstream.hpp
-    ../extern/zstr/zstr.hpp
     interfaces/highs_c_api.h
     io/Filereader.h
     io/FilereaderLp.h
-- 
2.53.0