How is damage assigned with creatures with menace and death touch?

[Garebear_Gaymer]

Is damage cause by an attacking creature with menace split between both defending creatures?

If your opponent has a 5/2 creature with menace and death touch and is attacking and I block with a 4/5 and a 6/7, is damage of the attacking creature split causing both blocking creature to die from death touch, or does the first assigned blocker receive all the damage and die?

[FourDogsinaHorseSuit]

Is damage cause by an attacking creature with menace split between both defending creatures?

If your opponent has a 5/2 creature with menace and death touch and is attacking and I block with a 4/5 and a 6/7, is damage of the attacking creature split causing both blocking creature to die from death touch, or does the first assigned blocker receive all the damage and die?

Menace has no impact on damage asignments. It's a restriction on blocking. Once blocked (by two or more creatures) the menace word becomes meaningless.
The real wrinkle here is deathtouch:
When assigning damage, ANY amount of damage from a deathtouch creature is lethal. So:

Your op attacks with their 5/2.
You block it with a 4/5 and a 6/7.
Your op arranges the two creatures in the order they like to deal damage.
Let's say they do the 4/5 first and then the 6/7.
They must assign lethal damage to the first creature before they can assign any damage to the second. Because deathtouch makes 1 damage lethal your op can deal any number between 1-5 to the 4/5 and then deal whatever's left to the second creature (so: 5 and 0, 1 and 4, 2 and 3, 3 and 2, 4 and 1 are all legal)

Normally you're right: Because there's 5 power and 5 toughness, they have to deal all 5 to the 4/5 and can't deal any to the 6/7. (but this isn't normally. This is deathtouch)