Nuclear modification factor ($Q_{\rm{pPb}}$) of \fzero as a function of $p_{\rm{T}}$ in p--Pb collisions at \snn = 5.02 TeV for different multiplicity classes. The multiplicity class is defined with the ZNA, which is the ZN placed on the Pb-going side. Statistical and systematic uncertainties are shown as error bars and boxes, respectively. Black boxes around unity represent the binary collision scaling uncertainties. The $Q_{\rm{pPb}}$ of charged hadrons  are reported for comparison.