fast necessitates manual control -> more semantics for low level control) that need to be expressible, ie: more complex
easy to understand, maintain -> computer does more work for you to "figure things out" in a way that simply can't be optimal under al conditions.
TLDR: what you're asking for isn't really possible without some form of AGI
What languages are easy to understand and maintain, anyway?
Id argue that python, elixir, ruby and all manner of languages are easy to understand and maintain. I dont' have to think about memory management or buffer overuns. its much easier to avoid race conditions since I'm not stressing about low level details.
by that same definition, rust is pretty easy to maintain. I won't say its easy to write though.