A good & reputable obedience class should be very usefull to you & both of your dogs. it will help with basic commands, socialization, bonding, fun & excesize! Please look into it!

Are they both spayed/neutered? If not I would get it done asap as it could help, & the sooner the better the chances of it helping.

wolfie gave great advice!

Also to help make both dogs happy, pay attention to who is the leader (you should always be the pack leader) but for ex. I think from your response that the Lhasa is the leader so pet him first, feed him first, give him his treat first etc. etc.
But to help them get along better take them for a walk at the same time (but attatch the leash to the Lhasa first).

Ignore bad behavior & PRAISE ALL good behavior!!! When you are petting one & the other is dealing with it well (even for a second) praise, as soon as one gets jealous ignore that one, don't even look or talk to that dog, as soon as that one calms down praise him/her.

good luck!