  We report electron transport studies of a thin InAs-Al hybrid
semiconductor-superconductor nanowire device using a four-terminal design.
Compared to previous works, thinner InAs nanowire (diameter less than 40 nm) is
expected to reach fewer sub-band regime. The four-terminal device design
excludes electrode contact resistance, an unknown value which has inevitably
affected previously reported device conductance. Using tunneling spectroscopy,
we find large zero-bias peaks (ZBPs) in differential conductance on the order
of $2e^2/h$. Investigating the ZBP evolution by sweeping various gate voltages
and magnetic field, we find a transition between a zero-bias peak and a
zero-bias dip while the zero-bias conductance sticks close to $2e^2/h$. We
discuss a topologically trivial interpretation involving disorder, smooth
potential variation and quasi-Majorana zero modes.
