[Dev Help] Is it possible to hook into methods that are running in System Service?

Hi, I'm new to Xposed and I wanted to hook a method in class "com.android.server.am.ActivityManagerService" .

Since this class runs at a very early stage on system boot as a system service, I chose to use "initZygote" to hook into this method. However, I'm not sure it is possible to really hook into the method. If so, what is the classloader here if I wanted to use findAndHookMethod() to change the function behaviour?