add z-image docs

Author: leejet

README.md

@@ -45,6 +45,7 @@ API and command-line option may change frequently.***
     - [Chroma](./docs/chroma.md)
     - [Chroma1-Radiance](./docs/chroma_radiance.md)
     - [Qwen Image](./docs/qwen_image.md)
+    - [Z-Image](./docs/z_image.md)
   - Image Edit Models
     - [FLUX.1-Kontext-dev](./docs/kontext.md)
     - [Qwen Image Edit/Qwen Image Edit 2509](./docs/qwen_image_edit.md)
@@ -129,6 +130,7 @@ If you want to improve performance or reduce VRAM/RAM usage, please refer to [pe
 - [🔥Qwen Image](./docs/qwen_image.md)
 - [🔥Qwen Image Edit/Qwen Image Edit 2509](./docs/qwen_image_edit.md)
 - [🔥Wan2.1/Wan2.2](./docs/wan.md)
+- [🔥Z-Image](./docs/z_image.md)
 - [LoRA](./docs/lora.md)
 - [LCM/LCM-LoRA](./docs/lcm.md)
 - [Using PhotoMaker to personalize image generation](./docs/photo_maker.md)

assets/z_image/bf16.png

@@ -0,0 +1,28 @@
+# How to Use
+
+You can run Z-Image with stable-diffusion.cpp on GPUs with 4GB of VRAM — or even less.
+
+## Download weights
+
+- Download Z-Image-Turbo
+    - safetensors: https://huggingface.co/Comfy-Org/z_image_turbo/tree/main/split_files/diffusion_models
+    - gguf: https://huggingface.co/leejet/Z-Image-Turbo-GGUF/tree/main
+- Download vae
+    - safetensors: https://huggingface.co/black-forest-labs/FLUX.1-schnell/tree/main
+- Download Qwen3 4b
+    - safetensors: https://huggingface.co/Comfy-Org/z_image_turbo/tree/main/split_files/text_encoders
+    - gguf: https://huggingface.co/unsloth/Qwen3-4B-Instruct-2507-GGUF/tree/main
+
+## Examples
+
+```
+.\bin\Release\sd.exe --diffusion-model  z_image_turbo-Q3_K.gguf --vae ..\..\ComfyUI\models\vae\ae.sft  --llm ..\..\ComfyUI\models\text_encoders\Qwen3-4B-Instruct-2507-Q4_K_M.gguf -p "A cinematic, melancholic photograph of a solitary hooded figure walking through a sprawling, rain-slicked metropolis at night. The city lights are a chaotic blur of neon orange and cool blue, reflecting on the wet asphalt. The scene evokes a sense of being a single component in a vast machine. Superimposed over the image in a sleek, modern, slightly glitched font is the philosophical quote: 'THE CITY IS A CIRCUIT BOARD, AND I AM A BROKEN TRANSISTOR.' -- moody, atmospheric, profound, dark academic" --cfg-scale 1.0 -v --offload-to-cpu --diffusion-fa -H 1024 -W 512
+```
+
+<img width="256" alt="z-image example" src="../assets/z_image/q3_K.png" />
+
+## Comparison of Different Quantization Types
+
+| bf16 | q8_0 | q6_K | q5_0 | q4_K | q4_0 | q3_K | q2_K|
+|---|---|---|---|---|---|---|---|
+| <img width="256" alt="bf16" src="../assets/z_image/bf16.png" /> | <img width="256" alt="q8_0" src="../assets/z_image/q8_0.png" /> | <img width="256" alt="q6_K" src="../assets/z_image/q6_K.png" /> | <img width="256" alt="q5_0" src="../assets/z_image/q5_0.png" />  | <img width="256" alt="q4_K" src="../assets/z_image/q4_K.png" /> | <img width="256" alt="q4_0" src="../assets/z_image/q4_0.png" /> | <img width="256" alt="q3_K" src="../assets/z_image/q3_K.png" /> | <img width="256" alt="q2_K" src="../assets/z_image/q2_K.png" /> |