Mixing two different types of Enfamil formulas together is perfectly fine.
When you mix the two different Enfamil formulas you should mix them together using 1/2 one type and 1/2 the other type to make the formula.
You can also mix Enfamil formula with other brands of formula as long as you mix them half together it will be okay.
Some babies though may only drink one brand or type of formula and mixing them together may prevent the baby from wanting to drink it.
But you certainly can try and if the baby doesn't drink it or refuses the bottle then just mix them up their regular formula and they'll be okay.