There is no easiest way. You just need to find two dragons which collectively hold all three of the poo dragon's elements and breed them. This will form the possibility of getting a poo dragon. Breeding outcomes are never a guarantee, unless you breed two of the same elemental dragon, which always produces that elemental dragon.
the reason snowflake didnt come out is not because of which way u put them to breed to make snowflake u simply have to have a lvl 10 or higher terra and ice ... if there not 10 or higher u will never get a snowflke no matter how many times u try... take itfrom me i got it on my firest try u could check my city out... also iwanan get him to lvl 20 n i only have one alpine