After a lot of different solutions finally I found a really nice working solution for both leaning and zooming both with tracker (TrackIR or FTNoIR) z-axis.
DCS World give your really nice feature which I didn't try before which is modifier with switch/latch option. What i did is
Create a modifier with switch option. I used Scroll Lock as switch/Latch modifier as it is not used
If you like lean by default then use z-axis for lean without modifier
Then create zoom z-axis with modifier that you have created above
What is the plus point now you just toggle scroll lock button which will switch your z-axis to either zoom or lean.
Note: This technique don't interfere with your other controls that you set on HOTAS. I tested it with Huey
I updated the first post for new comers.