Process for preparing a zeolite composite material composed of a mixture of zeolites of AFX structure type and of BEA structure type, comprising at least the following steps: i) mixing, in aqueous medium, of a FAU zeolite having a SiO 2 /Al 2 O 3 mole ratio of between 30 and 100 with at least one zeolite of FAU structure type having a SiO 2 /Al 2 O 3 mole ratio of between 2 and 30 (upper limit excluded), and in which the mathematical parameter, P ze, corresponding to the mass percentage of the FAU zeolite with an SiO 2 /Al 2 O 3 mole ratio of between 30 and 100, in its anhydrous form (expressed in %) in the mixture of FAU zeolites, multiplied by the SiO 2 /Al 2 O 3 mole ratio of said same FAU zeolite with an SiO 2 /Al 2 O 3 mole ratio of between 30 and 100, is such that: 3250 < P ze < 7200, of at least one organonitrogen compound R, chosen from 1,5-bis(methyl-piperidinium)pentane dihydroxide, 1,6-bis(methylpiperidinium)hexane dihydroxide, 1,7-bis(methylpiperidinium)heptane dihydroxide, and mixtures thereof, and of at least one source of at least one alkali metal and/or alkaline-earth metal M of valency n, n being an integer greater than or equal to 1, the reaction mixture having the following molar composition: (SiO 2) / (Al 2 O 3) of between 30 and 80, H 2 O/ (SiO 2) of between 1 and 100, R/ (SiO 2) of between 0.01 and 0.6, M 2/n O/ (SiO 2) of between 0.005 and 0.45, in which SiO 2 is the molar amount of SiO 2 provided by all the zeolites of FAU structure type introduced into the mixture, Al 2 O 3 is the molar amount of Al 2 O 3 introduced by all the zeolites of FAU structure type introduced into the mixture, H 2 O the molar amount of water present in the reaction mixture, R the molar amount of said organonitrogen compound, M 2/n O being the molar amount of M 2/n O provided by all the FAU zeolites and by the source of alkali metal and/or alkaline-earth metal, up to the production of a homogeneous precursor gel; ii) hydrothermal treatment of said precursor gel obtained from step i) at a temperature of between 120°C and 220°C, for a time of between 12 hours and 15 days. i) mixing, in aqueous medium, of a FAU zeolite having a SiO 2 /Al 2 O 3 mole ratio of between 30 and 100 with at least one zeolite of FAU structure type having a SiO 2 /Al 2 O 3 mole ratio of between 2 and 30 (upper limit excluded), and in which the mathematical parameter, P ze, corresponding to the mass percentage of the FAU zeolite with an SiO 2 /Al 2 O 3 mole ratio of between 30 and 100, in its anhydrous form (expressed in %) in the mixture of FAU zeolites, multiplied by the SiO 2 /Al 2 O 3 mole ratio of said same FAU zeolite with an SiO 2 /Al 2 O 3 mole ratio of between 30 and 100, is such that: 3250 < P ze < 7200, of at least one organonitrogen compound R, chosen from 1,5-bis(methyl-piperidinium)pentane dihydroxide, 1,6-bis(methylpiperidinium)hexane dihydroxide, 1,7-bis(methylpiperidinium)heptane dihydroxide, and mixtures thereof, and of at least one source of at least one alkali metal and/or alkaline-earth metal M of valency n, n being an integer greater than or equal to 1, the reaction mixture having the following molar composition: (SiO 2) / (Al 2 O 3) of between 30 and 80, H 2 O/ (SiO 2) of between 1 and 100, R/ (SiO 2) of between 0.01 and 0.6, M 2/n O/ (SiO 2) of between 0.005 and 0.45, in which SiO 2 is the molar amount of SiO 2 provided by all the zeolites of FAU structure type introduced into the mixture, Al 2 O 3 is the molar amount of Al 2 O 3 introduced by all the zeolites of FAU structure type introduced into the mixture, H 2 O the molar amount of water present in the reaction mixture, R the molar amount of said organonitrogen compound, M 2/n O being the molar amount of M 2/n O provided by all the FAU zeolites and by the source of alkali metal and/or alkaline-earth metal, up to the production of a homogeneous precursor gel; ii) hydrothermal treatment of said precursor gel obtained from step i) at a temperature of between 120°C and 220°C, for a time of between 12 hours and 15 days.