You can have multiple jobs running at the same time. The easy way to do it is to have a single text file with two jobs in it, like this:

{
-name my_job1
-action -print running job 1
-command job1.bat
# do this every 8 hours
-action -inc 0 8 0 0
}

{
-name my_job2
-action -print running job 2
-command job2.bat
# do this every 4 hours
-action -inc 0 4 0 0
}