The zoom has two sample rate options:
44.1 kHz and 48.0 kHz. When you create a new project you must choose one of the two options, by default it is set to 44.1kHz. When using wave files in Zoom, the sampling rates must match or Zoom will not detect your .wav file on your SD storage. It will see the files on a USB storage device, but when you try to import the .wav file, you will get an invalid file format if the .wav sample rate does not match your project sample rate. Also, if you select the higher sample rate of 48.0 kHz, then your Zoom effect capabilities will be lost as they are only compatible at the 44.1 kHz sample rate project and .wav file choice.