Mask tracking: cutout window shows next video (PrPro)

Goal
I have Video A (an MP4) where a specific area needs to become a moving masked “window” that reveals Video B underneath. The mask/window needs to track smoothly as the shot moves/zooms. Video A ends, and then Video B continues full-frame.

What I need you to do
- Create a tracked/animated mask in Adobe Premiere Pro (mask path keyframes or tracking workflow) so the chosen area is transparent/holes through to Video B beneath.
- Ensure the masked area stays aligned during movement/zoom (no slipping).
- At the end of Video A, Video B continues normally (standard cut to full screen, or keep it simple and clean).

Deliverables
- Return a Premiere Pro project file (.prproj) with the masking fully set up (so I can swap/replace Video B and continue editing).
- Include any required linked assets (or use proxies and tell me exactly how to relink).
- If you use any plugins/effects, you must tell me — preferably no paid plugins.

What I will provide
- Video A (source clip - see screenshot attached)
- Video B (the clip that should appear through the mask)
- A reference screenshot / timestamp of the exact area to cut out (and I can mark it clearly)

Quality requirements
- Clean mask edges
- No obvious jitter / drifting
- Plays back correctly and exports correctly