Detection efficiency of double eclipsing binaries by number of data points and apparent magnitude. Left: cumulative histogram for the number of data points per light curve. After passing a threshold of approximately 1000 data points there is a significant increase in the quadruple detection efficiency. Note that the plateau and discontinuity at around 2000 data points is a result of the ZTF survey strategy. Right: cumulative histogram for the magnitude of stars for the complete sample and quadruple candidates in the magnitude range 13–20.5. We see that for stars fainter than G ≳ 18 the quadruple detection efficiency rapidly approaches zero. The sharp increase at G ≈ 15 is not fully understood.