  We studied the effect of external pressure on the optical response of the
nodal-line semimetal candidate ZrSiTe by reflectivity measurements. At
pressures of a few GPa, the reflectivity, optical conductivity, and loss
function are strongly affected in the whole measured frequency range (200-16500
cm$^{-1}$), indicating drastic changes in the electronic band structure. The
pressure-induced shift of the electronic bands affects both the intraband and
interband transitions. We find anomalies in the pressure dependence of several
optical parameters at the pressures $P_{c1}$$\approx$4.1 GPa and
$P_{c2}$$\approx$6.5 GPa, suggesting the occurrence of two phase transitions of
either structural or electronic type.
