zapwallettxes is only for Bitcoin Core.

In Armory, go to Help > Clear All Unconfirmed and then restart Armory. This will have Armory forget about your unconfirmed transactions so you can respend the inputs. Once Armory has started again, just make the transaction as you normally would but include a higher fee. You may run into an issue where Bitcoin Core will reject your transaction because it still remembers the original. In that case, you will need to stop Bitcoin Core, find the mempool.dat file, and delete that file. Then start Core and Armory again.