@echo off & setlocal enabledelayedexpansion

set file1=%1
set file2=%2
set file3=%3
set sk=
set c=0

if exist %file3% (set v=APPENDING TO) else (set v=CREATING)
echo %v% %file3%
   
for /f "tokens=*" %%a in (%file1%) do (
set x=%%a
call :xx
set /a c+=1
set sk=skip=!c!
)
for /f "%sk%  tokens=*" %%a in (%file2%) do >>%file3% echo.%%a
goto :eof
   
:xx
for /f "%sk% tokens=*" %%b in (%file2%) do (
set out=%%b
>>%file3% echo !x!   
>>%file3% echo %%b
goto :eof
)
>>%file3% echo !x!