You should be able to drag the corners of the PiP window to enlarge this window if that is what you mean.

Isn't that working for you ?

Thank you for answering! Yes, I can enlarge the PiP window but cannot zoom without changing the size of window.

The PiP player is fixed to the size of the window, so you would lose content if you zoom the player content without increasing the size. The only way to make the player larger is by increasing the PiP window dimensions. I'm surprised if that was possible previously, so maybe they fixed this. I notice that in 97 the layout of the PiP windows has changed and the play/pause and mute and unpip button now appear at a control bar at the bottom instead of overlaying the player area.