I am so sorry to hear your overwhelmed. I now they can be a lot of work but dont give up, it will get much easier.
I have 2 yorkies and I really enjoy them both but they may be older than yours, they are 9mo and 8mo old. Missy was easy to train but Max took a little longer.
I always seperate them when teaching them to sit, come and do any tricks. Once I get one of them to learn the new trick I would work on both at the same time. They have both done really well and I think in time your two will
Good luck, keep working with them and one day they will surprise you and catch on