This is a very simple combination. All you need to know is :
How to do the piston drops
How to do the Omi
No to combine them, think of a 2 count that actually has 3 strong beats: That would be the piston drop part. So 3 piston drops but only 2 counts. The 3 and 4 counts would be the Omi, so it will take 2 counts to do the Omi and the combo is a complete 4 count combo.