Are the Hotkeys inside of the VST version not working?
I couldn't do any zooming neither with the mouse nor with the +/- hotkeys.

There was a very old post on some other site (about 5 years old) about this topic. But it seems like it was never solved.
From what I know this is a common problem with "plugins".

Does someone know a workaround of some sort?
Or is it maybe just some setting that I have missed?

Because the host your running xt inside is the master, it retains the keyboard commands.