Over on the Nature Recordists list on Yahoo, Klas Strandberg, reports that he modified a Zoom H4 with good results. Klas is the maker of the Telinga microphone systems. He removed the two mic capsules built into the H4, substituting a pair of his EM23 mics.
Klas reports that the mod H4 works well. Like others here have reported, Klas found the H4 needs an external power supply to avoid extraneous noises caused by the internal power unit.
Flintstone