I would assign a video to each of the "comic book" segments on the page.

Create a Vegas project for each of the videos and set the project properties to the pixel dimensions of the assigned segment.

Nest each segment project in the main project and us Track Motion to place in each segment position.

You can determine each segment pixel dimensions by "Saving a Snapshot to File" in Vegas and measuring it in a photo editor.

It sounds more complicated than it really is.    

Thank you for your answer. I tried to do what you advised me to do. 

I zoomed into the first segment of my page with the "track motion" button to get the desired size. I made a capture that I opened in Photoshop where I measured the dimensions of this segment (1156x1059 pixels). 

I opened a new project with dimensions 1156x1059 pixels where I imported my first video. I made a rendering. 

Then I opened my main project. I imported my video on a "child" track of the track where the comic book is located. When I move the position to the second segment with the "parent motion", I have the same problem, the page is cut off.

I feel like I have a problem with the size of my comic book page. If I zoom in and i move to another segment, my page is cuted off

Lose the Parent / Child relationship.

Cut (to transparency) the windows out of your Comic Page .jpg and save as .PNG with transparency.

Resize and locate your nested projects on lower tracks with Pan/Crop.

Here's a starter project that you can reverse engineer.

Here's what the first step looks like.

Thank you for your time John, I really appreciate your help. I can realize the first step.

Then it gets more complicated. If you zoom in on the flag video, you lose quality, this is the first problem.

Then when you want to move the camera from first segment to second segment, the whole thing has to move, which is why I made a parent track and a child track. But at that moment, my page is cut off when I use the parent track

This is exacly what I try to do :

Increase your main project pixel dimensions to 4096x2304. Change your sub-projects to provide the aspect ratio of your mask window but stay closer to your media source, 1920x1080, etc. or not more than your final delivery pixel dimensions. Use Pan/Crop and Track Motion if you have to. You may struggle with Vegas Pan/Crop limit, but it can be a lot closer to your goal.

I have to go do some actual work.

Thanks John, I will try

What I would try to do for that is create a large project in the dimensions of the borders. Or a close as possible to the frame limit in vegas. Put all the videos where they belong. Render that, then import that file into the actual timeline and pan and zoom around as needed. You can also easily add some 3D motion doing it that way like the first few clips here https://www.dropbox.com/s/di5t039wupj4001/REEL.mp4?dl=0

Interesting idea. But what are the dimensional limits? 

Interesting idea. But what are the dimensional limits? 

The maximum frame size is 4096×4096. It's not enoufh to put 9 videos in 1920x1080

Probably not but it might not look too bad and if you want to go full screen maybe replace them at those segments with the actual footage. Maybe with a border effect to match the panel?.

It's a little complicated. I feel like my solution is the simplest.

Place 9 videos in full screen on a track. 
On a parent track, place my mask with the boxes. 
And adjust the size of my mask to my first video, then move the whole thing with the parent track to a new box. 

The only problem is that once I move the whole thing with the parent track, my mask is cut off and I can't resolve this. 
 

With Vegas Pro's current 4096 x 4096 project size limitation the maximum resolution possible with my method is 960x540 for the video in the rectangular mask and 570 x540 for the video in the square mask.  

Project Here 

It looks like this...

Edit: Some devices can't /won't play 4096x2304 so I replaced with a 1080p version.

Your method would be simpler if it worked.

With Vegas Pro's current 4096 x 4096 project size limitation the maximum resolution possible with my method is 960x540 for the video in the rectangular mask and 570 x540 for the video in the square mask.  

Project Here 

It looks like this...

Your method would be simpler if it worked.

Yes, indeed, that's the problem. Great work, John, thanks. I made a rendering of your master composition, I can't see if you lost quality when zooming in full screen ?

It might not be quite what you were looking for or maybe a little more than you wanted to spend, but some of these templates are worth the money strictly in terms of the time and headaches they save. Also, when you get the template, it is essentially a masterclass in Vegas because you can see exactly how they did it and usually I learn a lot in seeing that.

Photowall seems to be the closest to what you are wanting to do. But there may be some other ones in there you might like better.

https://vegasaur.com/sony-vegas-templates

It might not be quite what you were looking for or maybe a little more than you wanted to spend, but some of these templates are worth the money strictly in terms of the time and headaches they save. Also, when you get the template, it is essentially a masterclass in Vegas because you can see exactly how they did it and usually I learn a lot in seeing that.

Photowall seems to be the closest to what you are wanting to do. But there may be some other ones in there you might like better.

https://vegasaur.com/sony-vegas-templates

 

Price is not a problem if template can match. I really need book look like wall, I d'ont know if photowall can do this

Just dealing with the grid (or mask as you call it) and not using any images to fill the black boxes, I think what you are saying is that if you use pan/crop to zoom in on a particular box in your grid, the white lines appear to be cut off on one side (truncated) and do not bleed off the edge of the screen as you would like.  I think I see this problem in zooming in on your grid (mask) using pan crop but I don't see this happening when using track motion or parent motion to zoom in on the grid. 

But is this the main problem you are having?

Just dealing with the grid (or mask as you call it) and not using any images to fill the black boxes, I think what you are saying is that if you use pan/crop to zoom in on a particular box in your grid, the white lines appear to be cut off on one side (truncated) and do not bleed off the edge of the screen as you would like.  I think I see this problem in zooming in on your grid (mask) using pan crop but I don't see this happening when using track motion or parent motion to zoom in on the grid. 

But is this the main problem you are having?

Hi xberk, yes it's the main problem, and it's happening because I have to zoom on grid first with pan crop or track motion before to use parent track to move all videos on grid

I'm able to zoom the grid using track motion while also using a matching track motion zoom for each image in each box. So you set each image in the box with track motion and you zoom on the grid via track motion and also zoom the image in each box to match the track motion of the grid. The time line looks like this.

This is a complex scheme that could run into trouble as you fill at nine boxes with images .. I tried Parent Motion and it is far easier to control but as you zoom in resolution in each box becomes a problem.

I'm able to zoom the grid using track motion while also using a matching track motion zoom for each image in each box. So you set each image in the box with track motion and you zoom on the grid via track motion and also zoom the image in each box to match the track motion of the grid. The time line looks like this.

This is a complex scheme that could run into trouble as you fill at nine boxes with images .. I tried Parent Motion and it is far easier to control but as you zoom in resolution in each box becomes a problem.

Yes it's a solution, but complex because I have a lot of video on each page, and a lot of elements on each video like images, lower third, texts ... it would be too long to implement with all these elements to move and zoom in, zoom out.

I think John's solution is the most effective