I am a beginning student in SFQ and the following opinion is my own, I speak for myself only.
There is no relationship whatsoever to zhan zhuang wich seems to be a nei gong system related to chinese internal(nei jia) martial arts.
In general I would say SFQ falls into the category of medical qigong. It's not related to martial arts in general and it's not really nei gong either as far as I can see - where nei gong is defined as a system designed to teach principles of internal martial arts in an even more abstract way than taijiquan for example.
SFQ is it's own system - it's a medical qigong system used for health/healing and I would say it's extremely effective for that. If there is anything I would compare it to it would be another medical qigong - the chiLel system of Dr. Pang Ming for example. http://www.chilel-qigong.com/
Or the methods of Dr. Zhi Gang Sha - another respected teacher of medical qigong. http://www.drsha.com/
As I pointed out in another thread there are different categories of qigong and I would put SFQ and other things like chiLel into the medical qigong category. These arts are great for your health but no they're not related to zhan zhuang.
I hope I've helped to answer your question, I am certainly not an expert in qigong.
