Thanks for answers,

I'm afraid, I didn't completely understand all of you about transliterating commands name. I don't want to do this.

I don't want to translate or transliterate command names.

I just want to transliterate text part of input.

I can't split commands and math input from text input, because there is inline math and commands are all around .

It is serious amount of switching. (ALT+ SHIFT keys), and when i'm thinking about what i should type(about subject) i forget to switch, and that's happening all the time.

Mojca, for 'ž'  i again have to switch keyboard. 

Also, Mojca probably the best understand what i want and that Serbian language can  be  written equally in  latin and cyrillic script.

Some people privately write in one script and some other people in another. So there is a lot of scripts in Serbia written in latin script.

But official is CYR. 

ОТ2 doesn't transliterate commands--- just text --- and i'm able to type 'zh' and 'ж' in the same file and he knows  what i want,

both input characters he treats the same. Even more Babel understand that too, and hyphenate words according the rules define in cyr.