This line fires event 'timezoom' and passes the value. I don't see what the handler does, what the value is, and I don't know how Scheduler is configured. Could you please modify any of our examples, do minimal changes to reproduce the issue, zip it up and attach here? Also please mention Scheduler version. How to ask for help is described here: viewtopic.php?f=35&t=772
This line looks correct at first glance. schedulerEngine is your scheduler instance, and zoomLevel is the property to change.
Could you please submit a small runnable testcase which shows the problem? You can apply minimal changes to one of our demos. Also please mention Scheduler version you're using.