You can convert to mp3 at different bitrates which will give you a better sound, but you wont notice the difference between wma and mp3 anyway through little ear phones... only if you have on a powerful soundsystem with bass. I find it easier using windows media 10 to rip to that and then sync all the files i want at once to the zen.
As much as i love my zen m... it eats battery life... ive known laptops that last longer than it, and i cant pretty much watch one movie and listen to 10 songs till it dies horribly. then i cant seem to half charge the battery... it just wont turn on till its fully charged.
It also goes a little screwy when i plug it into my laptop when its on standby (Power supply plugged in, not actually booted up)
AND no ac adapter?! whats going on... anyways sorry for that little rant, am getting annoyed with my zen hehe