~~~THE TASK~~~
Zombies got communication-problems because of their heterogeneity, so they defined a standard for their communication. We need to know how to decrypt their messages in order to successfully defeat them. Luckily, a friend of mine found one of those encrypted messages: 
0x1be15dc 77676058612 03062372 676 0x9542  0x2546c9ec  02614610  0x3b3154e5a0a923ff  
Hint: uppercase seems legit. credits: 100 +3 (1st), +2 (2nd), +1 (3rd)
~~~THE SOLUTION~~~
We see here some words, which are represented by 16-, 10- and 8-digit integers.Let's transform these integers, so each of them would be 36-digit. So, we get:
17 14 21 21 2435 24 22 11 18 14 2817 14 27 1418 28  29 17 14 10 12 12 14 28 28  15 21 10 1632 14 21 24 31 14 11 27 10 18 24 0
Each of the 'digits' may represent a digit (0-9) or an uppercase letter (A-Z). We know, that uppercase letters are legit. So, we try to find out the correspondence between our 'digits' and these letters.
We suppose that the first string is HELLO, so we get:
H - 17E - 14L - 21O - 24
We also think about rather a rare combination of double letters
10 12 12 14 28 28 
and this appears to be ACCESS.
So:
A - 10C - 12S - 28
Finally, we see, that each letter corresponds to the number 
9+i 
where i is the place of this latter in the alphabet. 
The whole message is:
HELLOZOMBIESHEREIS THE ACCESSFLAGWELOVEBRAIN0
(the final zero is strange).
We try WELOVEBRAIN0 and WELOVEBRAIN, but get a mistake. After a few attempts we find out that the flag is WELOVEBRAINZ.