How do I make tiled background zoomable?

I have a large map -> 10000,5000 <- with tiled grass all over it.

The game I am making has a vital function of zooming in and out, and, while every other sprite can just have a much bigger resolution (and smaller sprite size then it's res) and look good both faraway and zoomed; you are unable to do such a thing with tiled background.

How do I make so that the tiled background would not go blurry and ugly upon zooming into it?

Thank you in advance.

It needs to be on it own layer.

Scale the layer in away that its scale factor = 1 when the the others are zoomed in to the maximum allowed.

But then grass just stays the same; and other sprites look floating in empty space.

Also, what exactly is a "scale factor", because there are several scale properties in Construct.

Although I might have misunderstood you, let me test smth and get back to you.

UPDATE : Okay, although a genious idea; this does not work as well as you'd expect :

1. Grass is too small and looks odd

2. Everything now looks as in its floating on grass, not built on it (since grass's scale is now 0.5 when layout's scale is 1.0)

Any way else? Point sampling does the job extremely well, but it results in weird flickering on anything that moves smoothly, which hurts the eyes.

Other ideas?

1. Graphics issue, got to draw in right proportions.

2. You do not zoom proportional.

3. A scale factor is a number which scales, or multiplies, some quantity.

Why point sampling ? Are you making pixel art ?

Are you scaling each object individually ?

I am getting the idea that you are doing something totally not standard.

Gonna humble back off, might be better if you share a .capx.

Yes, I am macking a pixel art game (though with physics and correct collisions)

I am scaling the layout itself (+ layer 0 as you proposed)