I pushed a fix, so now if a new scene is created, a new corresponding zoom renderable will be associated with it (initially undefined, but it will get defined if a zoom block is used, making a new scene essentially have the zoom extension reset). Now, since the zoom renderable corresponds to the current scene, that means that if you pop a scene, the popped scene’s renderable will be destroyed along with it, and the old zoom layer will still be there upon returning to the previous screen.
To upgrade the extension, simply go into the javascript menu and click to open the Explorer, then scroll down to the extension and click the version number. It will then update it. The old version is v2.0.1 as shown below, and the new one is v3.0.3.
In the process of fixing this, I cleaned up stuff and made the extension mostly self-contained within a namespace (the enum is still separate to keep compatibility, so changes to the code of programs do not need to be made). So variable names and such within code should no longer conflict with the extension’s code.