It is never a good idea to send multiple tax returns and payments in the same envelope  --unless you enjoy waiting 2-3 ties as long for your returns to be accepted and processed.

Always put only ONE return and its supporting papers and payment in one envelope.

When mailing a printed return it is always a good idea to go to the Post Office and mail it 'Certified' with 'Return Receipt'.  That way you will have proof that they received it and when it was received.

 @retiree I would but the printout that turbotax provided has both forms together and I can't tell how to separate them.

Looks like you're stuck.

When you go to the 'Print Center' you should see a list of forms that will be printed by default.  However you should see a square check box at the beginning of each set of forms.  By deselecting the forms one at a time you should be able to then print only the remaining set of forms.  As a simple alternative you could simply print the forms twice; then manually you could select only the set to be mailed in each separate envelope

If you were to send both sets of forms in the same envelope you risk the tax department receiving the forms will get things confused.