# $ZZ^{(*)}$ decaying to leptons mass spectrum

I was looking the mass spectrum of the $ZZ^{(*)}$:

and I was wondering why the shape is the way it is.

The peak around 90 GeV is the single Z resonant, what is reason behind the slight peak in the range 100-160 GeV? Around the 200 GeV must be the on shell Z, right? (91 $\times$ 2 GeV). Is the high mass tail due to off-shell Z decay?