Context:The standard cosmological model is based on the simplifying assumptions of a spatially homogeneous and isotropic universe on large scales. An observational detection of their violation, at any redshift, would immediately indicate the breakdown of the aforementioned assumptions or presence of new physics. Aims: We quantify the ability of the Euclid mission, together with contemporary surveys, to improve the current sensitivity of null tests of the canonical cosmological constant Λ and cold dark matter (ΛCDM) model, in the redshift range 0 < z < 1.8. Methods: We consider both currently available data and simulated Euclid and external data products based on a ΛCDM fiducial model, an evolving dark energy model assuming the Chevallier-Polarski-Linder (CPL) parametrization or an inhomogeneous Lemaître-Tolman-Bondi model with a cosmological constant Λ (ΛLTB), and carry out two separate, albeit complementary, analyses: a machine learning reconstruction based on genetic algorithms and a theory-agnostic parametric approach based on polynomial reconstruction and binning of the data, in order not to make assumptions about any particular model. Results: We find that using the machine learning approach Euclid can (in combination with external probes) improve current constraints on null tests of the ΛCDM by approximately a factor of two to three, while in the case of the binning approach, Euclid can provide tighter constraints than the genetic algorithms by a further factor of two in the case of the ΛCDM mock, albeit in certain cases may be biased against or missing some features of models far from ΛCDM, as is the case with the CPL and ΛLTB mocks. Conclusions: Our analysis highlights the importance of synergies between Euclid and other surveys, which are crucial to provide tighter constraints over an extended redshift range, for a plethora of different consistency tests of some of the main assumptions of the current cosmological paradigm.