We present the results of a molecular survey of long period comets C/2021 A1 (Leonard) and C/2022 E3 (ZTF). Comet C/2021 A1 was observed with the Institut de radioastronomie millimetrique (IRAM) 30-m radio telescope in November-December 2021 before perihelion (heliocentric distance 1.22 to 0.76au) when it was closest to the Earth (~=0.24au). We observed C/2022 E3 in January-February 2023 with the Odin 1-m space telescope and IRAM 30-m, shortly after its perihelion at 1.11au from the Sun, and when it was closest to the Earth (~=0.30au). Snapshots were obtained during 12-16 November 2021 period for comet C/2021 A1. Spectral surveys were undertaken over the 8-13 December 2021 period for comet C/2021 A1 (8GHz bandwidth at 3mm, 16GHz at 2mm, and 61GHz in the 1mm window) and over the 3-7 February 2023 period for comet C/2022 E3 (2GHz at 2mm and 61GHz at 1mm). We report detections of 14 molecular species (HCN, HNC, CH_3_CN, HNCO, NH_2_CHO, CH_3_OH, H_2_CO, HCOOH, CH_3_CHO, H_2_S, CS, OCS, C_2_H_5_OH and aGg'-(CH_2_OH)_2_) in both comets. In addition, HC_3_N, and CH_2_OHCHO were marginally detected in C/2021 A1, and CO and H_2_O (with Odin) were detected in C/2022 E3. The spatial distribution of several species (HCN, HNC, CS, H_2_CO, HNCO, HCOOH, NH_2_CHO, and CH_3_CHO) is investigated. Significant upper limits on the abundances of other molecules and isotopic ratios are also presented. The activity of comet C/2021 A1 did not vary significantly between 13 November and 13 December 2021, when observations stopped, just before it started to exhibit major outbursts seen in the visible and from observations of the OH radical. Short-term variability in the outgassing of comet C/2022 E3 of the order of +/-20% is present and possibly linked to its 8h rotation period. Both comets exhibit rather low abundances relative to water for volatile species such as CO (<2%) and H_2_S (0.15%). Methanol is also rather depleted in comet C/2021 A1 (0.9%). Following their revised photo-destruction rates, HNCO and HCOOH abundances in comets observed at millimetre wavelengths have been reevaluated. Both molecules are relatively enriched in these two comets (~0.2% relative to water). Since the combined abundance of these two acids (0.1 to 1%) is close to that of ammonia in comets, we cannot exclude that these species could be produced by the dissociation of ammonium formate and ammonium cyanate if present in comets.