  The narrow-line Seyfert 1 galaxy I Zwicky 1 shows a unique and complex system
of ionised gas in outflow, which consists of an ultra-fast wind and a
two-component warm absorber. In the last two decades, XMM-Newton monitored the
source multiple times enabling the study of the long-term variability of the
various outflows. Plasma in photoionisation equilibrium with the ionising
source responds and varies accordingly to any change of the ionising
luminosity. However, detailed modelling of the past RGS data has shown no
correlation between the plasma ionisation state and the ionising continuum,
revealing a complex long-term variability of the multi-phase warm absorber.
Here, we present a new observation of I Zwicky 1 by XMM-Newton taken in early
2020 characterised by a lower X-ray flux state. The soft X-ray spectrum from
the RGS reveals the two components of the warm absorber with $\log \xi \sim
-1.0$ and $\log \xi \sim 1.7$. Comparing our results with the previous
observations, the ionisation state of the two absorbing gas components is
continuously changing, following the same unpredictable behaviour. The new
results strengthen the scenario in which the ionisation state of the warm
absorber is driven by the density of the gas rather than the ionising
luminosity. In particular, the presence of a radiation driven, inhomogeneous
clumpy outflow may explain both the variability in ionisation throughout the
years and the line-locked N V system observed in the UV band. Finally, the
EPIC-pn spectrum reveals an ultra-fast wind with an outflow velocity of $\sim
0.26c$ and ionisation parameter of $\log \xi \sim 3.8$.
