I'll spare you the details, but a follow up "That's great. However, please rewrite it in the style of Ernest Hemingway." delivers concise, yet obviously Hemingway-esque emails. Example here: https://pastebin.com/rrkCMd8c It works much better in a two-step process. If "Write this email in the style of Ernest Hemingway" is affixed to the original prompt, the model will generate prose at length, defeating the purpose of being concise.
"That's great. However, please rewrite it in the concise style of Paul Graham," of course, works even better.