Shénme-what Zěnme yàng-how is something/somebody Zěnme-how The occasions may vary...But in my opinion the English words above can represent the Chinese meaning.For example,你在干什么？（What are you doing) 这个电视节目怎么样？（How is the TV programme) 怎么打开这个盒子？（How can I open this box) You see...most are used in questions...but there can be exception. Hope my answer will help you...

Shénme: what ? What's that? What's up? Zěnme yàng : How is sth or sb? Do you like it or not? Sometimes it can be used in a little rude way , when sb say you should not do sth ,you reply Zěnme yàng , that means "so what? You want to fight with me or what?" Zěnme : What's up ? What happend? (when being asked , you are hoped to tell sth in detail)

什么= What 怎么 sometime mean “what happen ？”or “how do you think ?" and Could plug some words in the back . 怎么样, mean Things done or how this.

什么Shénme——what 怎么样Zěnme yàng——how about 怎么 Zěnme——how