Most of the problems in creating services by wrapping libraries in RPCs, in my experience, come from most libraries not supporting asynchrony, timeouts etc.

The zlib example is a bit baffling to be honest. If zlib goes in to an infinite 100% CPU loop, perhaps due to a zip bomb, you're still screwed as far as I can tell

A full RPC abstraction also gives you the opportunity to change out the backend implementation that this doesn't.