A giant and nonlinear Zeeman splitting in diluted magnetic semiconductors (DMS) offers a unique opportunity to examine quantum Hall ferromagnetism (QHF) since crossing of Landau levels (LL) can be achieved in moderately strong (Btot ≈ 1 T) total magnetic fields. We carried out magnetoresistance studies on modulation-doped, gated heterostructures of Cd1-xMnxTe/Cd1-yMgyTe:I. We put into evidence the formation of ISing quantum Hall ferromagnet with Curie temperature Tc as high as 2 K. QHF in our device is manisfested by anomalous magnetoresistance maxima, their hysteretic behavior, and time-dependent resistance, similar to earlier observations in III-V heterostructures. However, in our system these phenomena are much stronger, especially when either 2- or 1-, and 0+ LL are brought into coincidence. The magnitude of the QHF spikes depends dramatically on the history of the sample, shows hysteresis when either magnetic field or gate voltage are swept, stretched exponential-time evolution characteristic of glassy systems, and strong Barkhausen noise reflecting the dynamics of ferromagnetic domains. Our study indicates that these metastabilities stem from the electronic systems itself as an effect of slow dynamics of ferromagnetic domains, while the nuclear spin polarization plays a rather minor role.