At the moment there is no single face-to-face interview scheduled at McKinsey which I am aware of. If your application is not time-critical, you can think about postponing your application/interviews until a later point in time when again face-to-face interviews will be conducted. (Side note: to avoid any speculation, McKinsey will go back to the classical face-to-face interview format after COVID-19)
However, Zoom or any other video conferencing technology won't affect interview performance or your chances of securing an offer. Firstly, it's the same for all candidates and interviewers are also trained to conduct interviews professionally via Zoom (I consider a strong technology setup as a basic prerequisite nowadays, including a strong internet connection). Secondly, the interview format on Zoom is the same as in real-life interviews - no change from that perspective.
For you personally when referring to nervousness (and I now assume that the nervousness is more connected to your personality and character as opposed to a lack of interview preparation), I would rather see an advantage of Zoom interviews compared to face-to-face interviews, since you can conduct the interviews from an environment you are comfortable with (your home office or whatever place) and it's slightly less intensive from an interpersonal dynamics point of view.
Hope that helps - if so, please be so kind and give it a thumbs-up with the green upvote button below!