I think he meant to say that sometimes renaming aac to m4a works. So Might try on other format also. IMO
I'm sure this should have been covered here already, but if not...
Aiff and wav are just the containers for PCM data.
While the container is different (for example, .wav file can have timecode embedded, but cannot store artwork like .aiff), the audio data within in the container is EXACTLY the same.
File extensions identifie files as audio files to application, so they could be opened/played, but once the file is opened extension is of no consequence, but the flag identifying the start of PCM data (and headers/metadata) is. I suspect embedded OS's handle it differently, though.
Try a little experiment: change the extension of an .aif file to .wav and open it say in VLC. It will be played back just fine (even if the header is placed differently within those two file formats).
There WAS a chance that Z1 can handle .aif file playback, but does not recognise the extension as audio file extention and ignores them, unfortunately it currently cannot.
SOME players are known to produce bursts of noise when they try to play headers and metadata as audio (i.e. Walnut), we should consider ourselves lucky to not to have such an issue with Z1.
As has been previously suggested, XLD is a good free mac application to handle the conversion, the resulting files will be bit perfect:
https://sourceforge.net/projects/xld/
My apology because I had tried what you did there on my MAC however the file will not playback anymore unless I change it back to its default extension..... just to confirm, if my music file was originally .wav then it is definately able to be played back on Zishan Z1?