A missing iterator on itertools module?

Hello
Suppose I have these 3 strings:
s1 = "AZERTY"
s2 = "QSDFGH"
s3 = "WXCVBN"
and I need an itertor who delivers
A Q W Z S C E D C ...
I didn't found anything in itertools to do the job.
So I came up with this solution:
list(chain.from_iterable(zip("AZERTY", "QSDFGH", "WXCVBN")))
['A', 'Q', 'W', 'Z', 'S', 'X', 'E', 'D', 'C', 'R', 'F', 'V', 'T', 'G', 'B', 'Y', 'H', 'N']
Do you havbe a neat solution ?