Can I modify the default zombie model for singleplayer map ?

I want just modify him for have an other model. And if I can i want choose the model I want to replace .

I don't want use customs models...

So, it is possible ?

If not, can I just lower the arms of the zombie ?

Thanks you , if you answer this question...

Another alternative is possible.

If I have to use the CustomModels plugin,

then replace the white texture when there is no skin?

Thank you again, if you answer me ...

Sorry for the late answer, but theres /ModelScale to scale the model, but for lowering the arms and such, you may need the CustomModels plugin, i sincerely don't know about editing a model in Classicube besides 3D Modeling tools like Blender or Blockbench.

It's confusing what you're asking. If you just want a zombie with its arms lowered, you can find or upload a zombie skin and just put it on the normal humanoid model.
You can find the default ClassiCube zombie skin in here: https://static.classicube.net/default.zip
Then upload it to something like dropbox or imgur, and use the URL as the skin.
Or you can search the web for countless default Minecraft zombie skins.

I'm not trying to change the zombie skin but the original zombie model.

But I already have a little solution.

Thank you both for your answers.