Translation:How are you today?
In an attempt to find which shortcuts work, given the lack of an official "you (plural)" in the English language and not wanting to type out "you guys", I've found that although "y'all" is considered acceptable, "How y'all doing today" is not accepted, but "How're y'all doing today" is :D
Thats because that is only an American word, and if you extend it, "How y'all doing today" becomes "How you all doing today" This is wrong as it doesn't make grannatical sense, even though it might be slang However, "How're y'all doing today becomes "How are you all doing to day" This grammatically makes sense. Plus there is an English you (plural), it is "you all"
Originally, Old English had genders and had versions for pronouns that fell out of use.
"Thou" was used for singular and "You" was used for plural. An example of the use in singular would have been "Where art thou?" and now it is "Where are you?".
If you have ever heard any Willian Shakespear, no doubt you have heard of "Thou, Thy, Thee" before.
zen me yang, translates roughly to "how are things". A literal translation of ni jin tian hao ma would be you today good? (how are you today). It's two different ways of saying the same thing. In order to ask if someone is feeling well, you'd probably say something more like 你感觉怎么样？
The correct translation is "how are you [guys] today?" because of the character "你" in the phrase "你们". "你" means "you" and the phrase "你们" can be translated as "you all", "you guys", or "you girls". To say "how are they today?", either the character "他" or "她" would've been used in place of "你", depending on the gender makeup of the people being asked about.
@raphael - I'm just a learner myself; not a native speaker. Based on what I know, 怎么 means "how", and 怎么样 means "how is" or "how are" depending on context. e.g. How to say this = 这个怎么说, How is he = 他怎么样. As @sparkzi mentioned above, 样 = shape/appearance. So 怎么样 literally is "how appearance"? i.e. How is someone or something. That's what I think. Look forward to some expert native speaker's validation / correction.