I live in the UK and here in the UK the most common approach for a house front door is to have two different and separate locks.
One is known as a ‘night latch’ like this one http://www.yale.co.uk/en/yale/couk/productsdb/nightlatches/77---Traditional-Nightlatch/
The other is known as a mortice deadlock like this one http://www.diy.com/departments/yale-76mm-polished-chrome-5-lever-mortice-deadlock/198549_BQ.prd
The above mortice deadlock is superficially similar to an American style deadbolt but is not identical, one more obvious difference is that the bolt on a mortice deadlock is a rectangle while the bolt on an American deadbolt is more oval.
While there is a Z-Wave compatible night latch from Yale http://www.yale.co.uk/en/yale/couk/smart-living/connected-smart-locks/keyless-connected-smart-lock/ it was more difficult to find a smart i.e. Z-Wave compatible mortice deadbolt. I eventually found this one https://danalock.com/?page_id=35
Note: Since American deadbolts are defacto predominantly used in American - duh! - they are not available either in European Z-Wave compatible versions. This also necessitated looking for an alternative and as the Danalock is made in Europe it is of course compatible with European Z-wave frequencies.
The DanaLock is a slightly different form of mortice deadbolt lock in that it uses a euro profile lock mechanism but otherwise is similar to a standard mortice deadbolt including still having a rectangle shaped bolt and rebate. It is therefore an easy process to swap out the original mortice deadbolt. In fact even here in the UK euro profile mortice deadbolt locks are widely used although more typically for patio doors and commercial property doors.
So I now have a Z-Wave compatible night latch, and a Z-Wave compatible mortice deadbolt. I have been able to add both to my Smartthings hub, and the Smartthings app is able to operate both individually. What I would now like to do is get them linked so that when I unlock the night latch it automatically unlocks the mortice deadbolt i.e. the Danalock. I should add that I would be unlocking the night latch via its keypad or RFID tag and want this to be the trigger to unlock the Danalock.
I could probably do this via IFTTT but is there a way to do this in Smartthings?
It should be noted that the next step would be to also include the disarming of the alarm system so that when the Yale night latch is unlocked the alarm is disarmed and the Danalock is also unlocked. This sounds a bit too complex for IFTTT.
A final step would be to link the locking of the Danalock to arming the alarm system. (In this case it would not be necessary to include the Yale night latch as it automatically locks itself.)