Need help with the Burrow ability

I'm trying to make a zeppelin unit have the 'burrow' ability so that it can fire multiple missiles, according to the number of units within the zeppelin. However, I couldn't get the units to even load the zeppelin with the 'Load (Burrow)' ability. So then I tried doing the exact same thing with the 'Load (Goblin Zeppelin)' ability, and the units did load properly, but it didn't have the Burrow effect.
Any ideas?

Cargo Hold (Burrow)

That is the ability you're looking for.

I tried. Didn't work.

use my last post in other thread, i added trig designs!

Since the other thread is alive and well, I'm going to close this.