  To address the issue of the pseudogap in the superconducting state of the
high temperature superconducting cuprates, we studied the temperature dependent
redistribution of the spectral weight in the \textit{c}-axis polarized optical
spectra for underdoped YBa$_{2}$(Cu$_{1-x}$Zn$_{x}$)$_{3}$O$_{7-\delta}$ single
crystals with $x=0,0.007,$ 0.012, and 0.04. It was found that for Zn
substituted samples, the spectral weight transfer to the high energy region,
which characterizes the pseudogap state, continues even below the
superconducting transition temperature (\textit{T}$_{c}$), indicating the
coexistence of the pseudogap and the superconducting gap. Moreover, the
observation of the pseudogap in the Zn-doped non-superconducting sample gives
evidence that the pseudogap is not a precursor of superconductivity.

Superconductivity