Feedback on Pacing in Zones

I’m trying to dial in my runs a bit more, and looking for some feedback on pacing in tempo, fast finish and faster intervals… Is it the average pace during the time period that matters?
When I transition to intervals it takes a bit of time for me to increase the pace into the new zone, and sometimes there is some up and down of speed (incline, fatigue). Is it the overall average pace during the interval or do I need to focus more on transitioning faster and staying steady in zones, 3, y, and 4 specifically? Thanks very much in advance for feedback!