Hi...
Your zoom feature was an excellent idea and absolutely required with the low resolution of current VR units. But, I find it to be incredible nausea and headache inducing.
Might I suggest that you take a look at what google earth VR did on their recently released VR software? When you transition from standing to "flying" they significantly reduced the FOV. This seems to be enough disrupt your sense of presence and, in my case, it completely eliminated the nausea.
Just a suggestion.