We present the results of a continuing survey to detect Ly alpha emitting galaxies at redshifts z similar to 9: the z equals nine' (ZEN) survey. We have obtained deep VLT Infrared Spectrometer and Array Camera observations in the narrow J-band filter NB119 directed towards three massive lensing clusters: Abell clusters 1689, 1835 and 114. The foreground clusters provide a magnified view of the distant Universe and permit a sensitive test for the presence of very high redshift galaxies. We search for z similar to 9 Ly alpha emitting galaxies displaying a significant narrow-band excess relative to accompanying J-band observations that remain undetected in Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) optical images of each field. No sources consistent with this criterion are detected above the unlensed 90 per cent point-source flux limit of the narrow-band image, F-NB = 3.7 x 10(-18) erg s(-1) cm(-2). To date, the total coverage of the ZEN survey has sampled a volume at z similar to 9 of approximately 1700 comoving Mpc(3) to a Lya emission luminosity of 10(43) erg s(-1). We conclude by considering the prospects for detecting z similar to 9 Ly alpha emitting galaxies in light of both observed galaxy properties at z < 7 and simulated populations at z > 7.