Context : The nearby ultra-compact multiplanetary system YZ Ceti consists of at least three planets , and a fourth tentative signal .
The orbital period of each planet is the subject of discussion in the literature due to strong aliasing in the radial velocity data .
The stellar activity of this M dwarf also hampers significantly the derivation of the planetary parameters .

Aims : With an additional 229 radial velocity measurements obtained since the discovery publication , we reanalyze the YZ Ceti system and resolve the alias issues .

Methods : We use model comparison in the framework of Bayesian statistics and periodogram simulations based on a method by Dawson and Fabrycky to resolve the aliases .
We discuss additional signals in the RV data , and derive the planetary parameters by simultaneously modeling the stellar activity with a Gaussian process regression model .
To constrain the planetary parameters further we apply a stability analysis on our ensemble of Keplerian fits .

Results : We find no evidence for a fourth possible companion .
We resolve the aliases : the three planets orbit the star with periods of 2.02 d , 3.06 d , and 4.66 d. We also investigate an effect of the stellar rotational signal on the derivation of the planetary parameters , in particular the eccentricity of the innermost planet .
Using photometry we determine the stellar rotational period to be close to 68 d and we also detect this signal in the residuals of a three-planet fit to the RV data and the spectral activity indicators .
From our stability analysis we derive a lower limit on the inclination of the system with the assumption of coplanar orbits which is i _ { \mathrm { min } } = 0.9 deg .
From the absence of a transit event with TESS , we derive an upper limit of the inclination of i _ { \mathrm { max } } = 87.43 deg .

Conclusions : YZ Ceti is a prime example of a system where strong aliasing hindered the determination of the orbital periods of exoplanets .
Additionally , stellar activity influences the derivation of planetary parameters and modeling them correctly is important for the reliable estimation of the orbital parameters in this specific compact system .
Stability considerations then allow additional constraints to be placed on the planetary parameters .