Your MWE is not clear about the variables you want to align with each other. Please, make the variables unique and say which ones you want to align with each other, so you can get a helpful answer.
For centering, I think
align always centers the equations, but if you wish to control the spacing, you may consider
If you you don't care about aligning the second equation, then you need to go with
a &= b + c \quad &\\
x &= y + z & a &= b + c
a = b + c\\
a = b + c \quad a = b + c