it depends on if it uses the same format as CPC version.

Nebulus hard harder levels I was sure game basic levels were hard as rock.

Not so hard. Only at one level (one of the last) you can go astray. But all other has only one way (with minimal branching).
In my childhood I have only version with endless timer so I can freely explore all levels.
And at year 2005 I've beat DOS version without any cheating (at the 35 try in several days, or something). Later I've find out about another DOS version which contain additional harder levels.

https://www.youtube.com/watch?v=rc2MigzEYAU&ab_channel=AmstradiensChannel this looks impressive on CPC  even the screen size is really small

It's possible integrate to EP version of Nebulus hard levels ("Mission 2") from Nebulus DOS version?

it depends on if it uses the same format as CPC version.

I compared the format of the level data in the ZX and CPC versions - they are identical.

[ Guests cannot view attachments ]

For the DOS version, the level storage format is almost the same.

(white is same data)
[ Guests cannot view attachments ] [ Guests cannot view attachments ]

I can try to parse the level coding format (it's not like RAW or RLE compression - something hybrid) but there will be a problem with the fact that the height (and therefore amount of data) of the each tower may be different. And will be need to change the entry points of data for each level (I definitely can't handle this).