  Hybrid semiconductor-superconductor devices hold great promise for realizing
topological quantum computing with Majorana zero modes (MZMs). However,
multiple claims of Majorana detection, based on either tunneling or Coulomb
blockade (CB) spectroscopy, remain disputed. Here we devise an experimental
protocol that allows to perform both types of measurements on the same hybrid
island by adjusting its charging energy via tunable junctions to the normal
leads. This method reduces ambiguities of Majorana detections by checking the
consistency between CB spectroscopy and zero bias peaks (ZBPs) in non-blockaded
transport.Specifically, we observe junction-dependent, even-odd modulated,
single-electron CB peaks in InAs/Al hybrid nanowires (NWs) without concomitant
low-bias peaks in tunneling spectroscopy. We provide a theoretical
interpretation of the experimental observations in terms of low-energy,
longitudinally-confined island states rather than overlapping Majorana modes.
Our results highlight the importance of combined measurements on the same
device for the identification of topological MZMs.
