怎么样【zěnmeyàng】

怎么样 asks what something is like. After a noun it is the whole predicate, so it takes no 是.

• × 这个菜是怎么样 → 这个菜怎么样

怎么样 or 怎么

怎么样 asks what something is like; zěn me怎幺 asks by what method.

Proposing something

After a suggestion, 怎么样 asks the listener whether they agree, like "how about it?"

不怎么样

bù zěn me yàng不怎幺样 is a verdict, not a question: "not great". It's a mild way to say you didn't think much of something.