Hello again Chris!
Please download the files here:
Here is how the zoom work:
Click on one of the markers. There will be a zoom button right above the get directions button.
If you are not currently at the max zoom and you click that button, it will zoom into the max zoom. So, if you click it and it zooms in, then you click the minus sign to zoom out one and then click zoom again, it will zoom back in.
However, if you are current at the max zoom and you click it again, it will zoom out to th default minimum zoom, which is currently set to 10.
So, if you click zoom, it zooms in. Click it again and it zooms back out. Very simple.
The max and min zoom is set at lines 1083 and 1084 of stadiums.html. I believe the current settings are good, so you shouldn't have to change them. But if you want to, that is where you do so.
Let me know if you have any questions.
Please remember to rate my answer. Thank you so much and have a wonderful day!