2D distribution of galaxies (where the projected Dec covers a range of 1.5°) in one of the W4 field mock catalogues used in this work. Top: all galaxies in the reference mock catalogue (100% sampling rate, the redshift includes cosmological redshift and peculiar velocity). Middle: galaxies in the Test D mock catalogue (see Sect. 4.1 for more details). The catalogue includes ~35% of galaxies in quadrants (black points) with spectroscopic redshift, while the remaining 65% in quadrants and all the galaxies in gaps have a photometric redshift (red dots). Bottom: equal probability contours for the ZADE probability function P(z_i) (see Sect. 3.1 for details). Colour code is set according to the statistical weight w_ZADE. Red: w_ZADE ≥ 0.2, Orange: 0.1 ≤ w_ZADE < 0.2. Green: 0.05 ≤ w_ZADE < 0.1.