diff --git a/compat/crypt.h b/compat/crypt.h
index 46f2b670..41c6454c 100644
--- a/compat/crypt.h
+++ b/compat/crypt.h
@@ -25,12 +25,15 @@
    Encryption is not supported.
 */
 
-#ifndef _ZLIB_H
-#  if (ZLIB_VERNUM < 0x1270)
-    typedef unsigned long z_crc_t;
-#  else
-    typedef uint32_t z_crc_t;
-#  endif
+#ifndef ZLIB_VERNUM
+/* No zlib */
+typedef uint32_t z_crc_t;
+#elif (ZLIB_VERNUM & 0xf != 0xf) && (ZLIB_VERNUM < 0x1270)
+/* Define z_crc_t in zlib 1.2.6 and less */
+typedef unsigned long z_crc_t;
+#elif (ZLIB_VERNUM & 0xf == 0xf) && (ZLIB_VERNUM < 0x12df)
+/* Define z_crc_t in zlib-ng 2.0.7 and less */
+typedef unsigned int z_crc_t;
 #endif
 
 #define CRC32(c, b) ((*(pcrc_32_tab + (((int)(c) ^ (b)) & 0xff))) ^ ((c) >> 8))
diff --git a/compat/ioapi.h b/compat/ioapi.h
index 79cffc85..82507460 100644
--- a/compat/ioapi.h
+++ b/compat/ioapi.h
@@ -4,8 +4,12 @@
 
 #include <stdint.h>
 
-#ifndef _ZLIB_H
-//#include "zlib.h"
+#if !defined(_ZLIB_H) && !defined(ZLIB_H) && !defined(ZLIB_H_)
+#  if __has_include(<zlib-ng.h>)
+#    include <zlib-ng.h>
+#  elif __has_include(<zlib.h>)
+#    include <zlib.h>
+#  endif
 #endif
 
 typedef uint64_t ZPOS64_T;
diff --git a/compat/unzip.h b/compat/unzip.h
index 7c24b60a..0c081542 100644
--- a/compat/unzip.h
+++ b/compat/unzip.h
@@ -38,18 +38,6 @@ typedef void *unzFile;
 
 /***************************************************************************/
 
-#ifndef Z_ERRNO
-#define Z_ERRNO                         (-1)
-#endif
-#ifndef Z_DEFLATED
-#define Z_DEFLATED                      (8)
-#endif
-#ifndef Z_BZIP2ED
-#define Z_BZIP2ED                       (12)
-#endif
-
-/***************************************************************************/
-
 #define UNZ_OK                  (0)
 #define UNZ_END_OF_LIST_OF_FILE (-100)
 #define UNZ_ERRNO               (Z_ERRNO)
diff --git a/compat/zip.h b/compat/zip.h
index 5c1f1258..67f5a5b1 100644
--- a/compat/zip.h
+++ b/compat/zip.h
@@ -38,16 +38,6 @@ typedef void *zipFile;
 
 /***************************************************************************/
 
-#ifndef Z_ERRNO
-#define Z_ERRNO                         (-1)
-#endif
-#ifndef Z_DEFLATED
-#define Z_DEFLATED                      (8)
-#endif
-#ifndef Z_BZIP2ED
-#define Z_BZIP2ED                       (12)
-#endif
-
 #define ZIP_OK            (0)
 #define ZIP_EOF           (0)
 #define ZIP_ERRNO         (Z_ERRNO)
diff --git a/mz_crypt.c b/mz_crypt.c
index 0b068e0b..7a47ff20 100644
--- a/mz_crypt.c
+++ b/mz_crypt.c
@@ -34,11 +34,15 @@ int32_t mz_crypt_rand(uint8_t *buf, int32_t size) {
 
 uint32_t mz_crypt_crc32_update(uint32_t value, const uint8_t *buf, int32_t size) {
 #if defined(HAVE_ZLIB)
-    /* Define z_crc_t in zlib 1.2.5 and less or if using zlib-ng */
-#  if (ZLIB_VERNUM < 0x1270)
-    typedef unsigned long z_crc_t;
-#  else
+#  ifndef ZLIB_VERNUM
+    /* HAVE_ZLIB but no ZLIB_VERNUM? */
     typedef uint32_t z_crc_t;
+#  elif (ZLIB_VERNUM & 0xf != 0xf) && (ZLIB_VERNUM < 0x1270)
+    /* Define z_crc_t in zlib 1.2.6 and less */
+    typedef unsigned long z_crc_t;
+#  elif (ZLIB_VERNUM & 0xf == 0xf) && (ZLIB_VERNUM < 0x12df)
+    /* Define z_crc_t in zlib-ng 2.0.7 and less */
+    typedef unsigned int z_crc_t;
 #  endif
     return (uint32_t)ZLIB_PREFIX(crc32)((z_crc_t)value, buf, (uInt)size);
 #elif defined(HAVE_LZMA)