It is not possibly any longer to make a Macro that activates both because they have a Global Cooldown (GBC) the GBC interrupts the Macro. But there are still two ways to use it, but they are not really comfortable.
The first is:
/castrandom Trinket1, Trinket2
that Macro will use randomly one of the two trinkets so you will have to smash the button a lot of times ^^.
The second way is
/castsequence reset=1 Trinket1, Trinket2
This will start a sequence of "casts" so if you push the button twice it will use both of you're trinkets.
You will have to rename Trinket1 and Trinket2 into you're trinket names