diff --git a/modules/external/libSceZlib/README.md b/modules/external/libSceZlib/README.md
new file mode 100644
index 00000000..d76c9b14
--- /dev/null
+++ b/modules/external/libSceZlib/README.md
@@ -0,0 +1,23 @@
+# How to ZLib
+
+## ZLib thread
+From what I see, the Library should create separate thread for ZLib data processing. This thread should be put to sleep by condition variable, when there's no requests (and `sceZlibInflate` should signal this variable ofc).
+
+## sceZlibInitialize
+Creates the ZLib processing thread. Passed buffer should not be used, moreover should set it to `nullptr`.
+
+## sceZlibFinalize
+Terminates ZLib processing thread and destroys every active request in queue.
+
+## sceZlibInflate
+Function `sceZlibInflate` creates decompression request and puts it into queue. The thread should process all the requests and store unpacked data for each request to `dst` pointer set by inflate call. The created request should be stored to `reqId` pointer passed to inflate function.
+
+## sceZlibWaitForDone
+Game should call `sceZlibWaitForDone` to check if there's any ready to use inflated blocks, the library stores `reqId` for finished block and returns `Ok`. However there's a `timeout` parameter, this function should return `Err::Zlib::TIMEDOUT` if every decompression request is pending (or the queue is empty).
+
+## sceZlibGetResult
+This function returns the decompressed data length and decompression status for specified request. Probably it should lock the thread if data is not ready yet.
+
+
+## Notes
+* There's a hard `64 KiB` limit for decompressed block size, if the decompressed block exceeds this limit, the `sceZlibGetResult` should return `Err::Zlib::NOSPACE` error code.
diff --git a/modules/external/libSceZlib/codes.h b/modules/external/libSceZlib/codes.h
index f158822a..68d383b6 100644
--- a/modules/external/libSceZlib/codes.h
+++ b/modules/external/libSceZlib/codes.h
@@ -1,4 +1,17 @@
 #pragma once
 #include <stdint.h>
 
-namespace Err {} // namespace Err
\ No newline at end of file
+namespace Err {
+namespace Zlib {
+constexpr int32_t FATAL               = -2129526529;
+constexpr int32_t ALREADY_INITIALIZED = -2129526733;
+constexpr int32_t NOT_INITIALIZED     = -2129526734;
+constexpr int32_t TIMEDOUT            = -2129526745;
+constexpr int32_t NOT_SUPPORTED       = -2129526747;
+constexpr int32_t NOSPACE             = -2129526756;
+constexpr int32_t INVALID             = -2129526762;
+constexpr int32_t FAULT               = -2129526770;
+constexpr int32_t AGAIN               = -2129526773;
+constexpr int32_t NOT_FOUND           = -2129526782;
+} // namespace Zlib
+} // namespace Err
diff --git a/modules/external/libSceZlib/entry.cpp b/modules/external/libSceZlib/entry.cpp
index 7dcc8c9b..d72417dc 100644
--- a/modules/external/libSceZlib/entry.cpp
+++ b/modules/external/libSceZlib/entry.cpp
@@ -4,15 +4,51 @@
 
 LOG_DEFINE_MODULE(libSceZlib);
 
-namespace {} // namespace
+namespace {
+static bool     g_bInitialized = false;
+static uint64_t g_reqId        = 0;
+} // namespace
 
 extern "C" {
 
 EXPORT const char* MODULE_NAME = "libSceZlib";
 
-EXPORT SYSV_ABI int32_t sceZlibInitialize(const void* buffer, size_t length) {
+EXPORT SYSV_ABI int32_t sceZlibInitialize(const void* buffer, size_t len) {
+  if (g_bInitialized) return Err::Zlib::ALREADY_INITIALIZED;
   LOG_USE_MODULE(libSceZlib);
   LOG_ERR(L"todo %S", __FUNCTION__);
+  g_bInitialized = true;
   return Ok;
 }
-}
\ No newline at end of file
+
+EXPORT SYSV_ABI int32_t sceZlibFinalize() {
+  if (!g_bInitialized) return Err::Zlib::NOT_INITIALIZED;
+  LOG_USE_MODULE(libSceZlib);
+  LOG_ERR(L"todo %S", __FUNCTION__);
+  g_bInitialized = false;
+  return Ok;
+}
+
+EXPORT SYSV_ABI int32_t sceZlibInflate(const void* src, uint32_t srcLen, void* dst, uint32_t dstLen, uint64_t* reqId) {
+  if (!g_bInitialized) return Err::Zlib::NOT_INITIALIZED;
+  LOG_USE_MODULE(libSceZlib);
+  LOG_ERR(L"todo %S", __FUNCTION__);
+  *reqId = ++g_reqId;
+  return Ok;
+}
+
+EXPORT SYSV_ABI int32_t sceZlibWaitForDone(uint64_t* reqId, uint32_t* timeout) {
+  if (!g_bInitialized) return Err::Zlib::NOT_INITIALIZED;
+  LOG_USE_MODULE(libSceZlib);
+  LOG_TRACE(L"todo %S", __FUNCTION__);
+  return Err::Zlib::TIMEDOUT;
+}
+
+EXPORT SYSV_ABI int32_t sceZlibGetResult(uint64_t reqId, uint32_t* dstLen, int* status) {
+  if (!g_bInitialized) return Err::Zlib::NOT_INITIALIZED;
+  LOG_USE_MODULE(libSceZlib);
+  LOG_TRACE(L"todo %S", __FUNCTION__);
+  *status = -1;
+  return Err::Zlib::NOT_FOUND;
+}
+}