Complete beginner, I have been doing 5x a week 1 hour brisk walks maintaining a zone 2 heartrate the whole time. I can I add in 1 day per week of jogging at zone 4 for 30 seconds, and then walking for 1-2 minutes and repeat for 25 minutes? How can I improve the quickest?

Before I was doing 3-4x a week 2 mile runs which put me at zone 4 for 25 minutes each run. I was told it was too much so I slowed it down. Now I am brisk walking which puts me at about 140, i do these for an hour each session. I do this 5x a week. If I have been doing cardio for only a few weeks, can I put in a once a week session of jogging for 30-45 seconds then walking for 2 minutes? Any jog puts me at about zone 4-zone 5 heart rate. I have to brisk walk to keep in in zone 2. I love it all so far, and want to eventually run as a hobby, but I want to be able to train as efficiently as possible rn as a beginner. How would I go about this?