karabooo says:
... I don’t know how to do a combined effort. ...
You both roll and then we see how it went, it does tend towards the average, but also spreads the risk.
We could also let one character take the lead (it does look like that would be
Albeart given
Ezme's 'what he said') and the other player essentially 'helps'. This game does not have any 'Help' mechanic, I prefer it that way and prefer to have the players 'helping' action affect the fiction and therefore what can be done and what consequences we can expect.
These add up to the same thing, but, by the fiction, both characters are working on the same action.