The Tektronix 3 Series MDO and Keysight DSO/MSO 3000T X-Series use different techniques for making automated measurements.  The Tektronix 3 Series MDO calculates measurements and performs waveform math on its entire acquisition memory.  So, measurements don’t change based on zoom settings.  Measurements on the Keysight DSO/MSO 3000T can vary depending on zoom settings, as shown in this video.