A nooby question..

[TheMarioProductionz]

Hey animemusicvideo.org!

Well, I encountered one serious problem.. How to zoom in with camera or something and don't lose quality, because sometimes when I zoom in I even can see those squares.

Thanks in advance.

[mirkosp]

Well, there is only one way to always solve this, but it requires a huge amount of effort. Basically, you'd have to vector the scene you want to zoom in into. That way it'll look good regardless of how much you zoom in. However you can guess that takes a lot of effort to do.
Other valid solutions for high amounts of zoom ins don't exist. If it's a quick zoom, then motion-blur will make it look okay since it's not focused, but if you need to do a slow zoom to over 200%, then I doubt you can do much about it. When zooming in, you're basically upscaling your footage, thus the quality obviously gets lower since the pc has to try and interpolate data that does not exist, so it will end up blurry and all.
Possibly the "best" solution is upscaling the scene with avisynth first, by using nnedi3, doing some sharpening, and then loading that in your program and start from a zoom out (since the image will now be bigger) and then zoom in to the needed amount. However upscaling is bad, so if you can avoid it, please do.
The best thing I can recommend you is to either keep zooms to low amounts (possibly 120% or so at the very most) and to look for other scenes to use if the required amount would be bigger.

[Niotex]

As Mirko stated it is impossible to retain optimal quality when zooming in. However there are certain ways of masking this via things like motion/radial blurs. These solutions only work for quick zoom cut/transitions though. If you are looking to zoom in on a piece of footage and keep it zoomed in, then you will either have to deal with the stretched pixels or as Mirko suggested convert the scenes to vector. I would personally however avoid both those options.

If you have any further questions or are considering vectorization I'll be happy to aid you.

[Eake4]

Niotex and Mirko has pretty much covered it all. I would recommend a fast zoom in with a blur however if your video needs a lingering zoom then theres really no choice but to vector it.