Hi, brendanbowlerxyz12345!
I've been doing a bit of experimentation myself along this line, I've found that if you crop and zoom on any portion of the clip, the cropped/zoomed portion will be blurry so it wouldn't be advisable to use the effect too often in a video.
How I did mine was this way, I used a clip of a steam loco passing by(not my camerawork but from a friend):
1) Find and select the wanted portion of video to be zoomed & cropped.
2) Find a suitable starting point where the subject first appears, click on and drag the right-side yellow tab of the scrubber, out to the point where the subject is out of shot. The portion of the video will be highlighted in yellow. Copy(Ctrl+C) the highlighted portion, making note of the frame where the highlighted area begins, it's at this point where you'll eventally paste the copied portion.
4) For the moment, paste the copied portion of the clip at the end of or just beyond the end of the clip*, then, highlight and cut the copy into clipboard(Ctrl+X). *There's a reason for this which I'll explain near the end of the post.
5) Now the copy is in clipboard, play the clip to the point where you noted the effect should begin, click on Video Track 2, paste the copy from clipboard at that point(Ctrl+V). Using modify, resize the pasted copy and position on the screen where you want it to be.
6) With the clip resized and positioned, select Power Tools then Crop & Zoom, adjust the crop to remove unwanted background at the start of the effect, then at the end, and then, with some tweaking, at various points through the effect(inserting keyframes as necessary). As I said at the top, the cropped and zoomed image will be blurry, there's no getting around that, and attempt to improve the sharpness might result in the image looking worse, so you'll just have to wear the blurry image.
*Now to the copying and pasting issue. After copying, paste at, or just beyond end of clip first, then cut into clipboard. I've found that an attempt to paste directly to the PiP track(Video Tr.2) results in the original being split at the point where I paste. You may find that usefull, I much prefer to note down the point on the timeline where the paste should be made before I start the "process" of zoom/crop/size adjust/positioning. There's method to my madness.
So there you have it. I've just recently started using this effect and this is what I've learned thus far about it. Again I'll say that because there's no getting around the blurryness of a cropped/zoomed image, it's advisable not to use the effect too often in a video, once, perhaps twice you can get away with it but any more can possibly detract from the overall quality you're chasing for your video.
Cheers!
Neil