As mentioned, there is a calorie burn per five minutes chart on your fitbit dashboard. In your case, you will be more interested in the color coded spiked--they represent the four different activity levels that fitbit will class each minute as. Gray is sedentary, teal is lightly active, yellow is fairly active and red is very active. Look and see if your running time is red, and your walking either yellow or red. The spikes will be higher or lower depending on intensity. The fitbit tracked intensity is mainly about how fast you are moving. I believe this would apply to the Zip, even though I have an "ultra".
You might even be able to see the specifics of your activity. This would be a little extra work for a zip user, and I am not sure if it would work since I do not have a zip. (I expect it would because I doubt the fitbit web accounts are really that different).
1--Go to your fitbit activity log, choose the option "activity record" (it is under "Today" and next to "browse")
2--If this works it will give you a form to fill out the activity name, start time and end time. Enter that information.
3--This should generate a record of whatever the fitbit tracked at that time--just like the record an Ultra or One user would see from using the timer button. I mainly use this if I fogot to use the timer and want to see the stats for a specific activity for some reason. I am not sure whether there is a difference in the sensitivity between the Zip and the higher end models (there may be from what I've read).
| December Minutes: 793