Just use a view with a fixed size, regardless of resolution, but considering aspect ratio. No need to zoom things or anything, you just place the sprites the same way as before.
For instance, if the aspect ratio is 4:3, then your view could be 1024x768, so players playing either at 640x480 or 1280x960 will see the exact same things on screen, stretched.
If your aspect ratio is 16:9, then you could make the view 1200x675 or any pair of numbers close to 1024x768 but being 16:9. It will not be the same as 4:3, but it will be close enough to not make any difference, so regardless if they are playing at 1366x768 or 1920x1080, they will always see 1200x675 on screen, again, stretched.
Either do that, or always use a view of size 1024x768 but add black lines to the sides depending of the aspect ratio. Personally, I prefer the former: I didn't buy a widescreen TV to play with huge black bars on the sides, didn't I?