Re: Zangoose training?
Well IVs go from 0-31 so 15 is about average. They're probably not considered good exactly, most people would probably try getting at least 25+ in important stats like Attack and Speed for Zangoose.
Personally I wouldn't worry about breeding for better IVs unless you're going to be battling competitively against other people and every stat point matters, but that's just me, since IV breeding can be quite a hassle and take a while...
At level 100, the difference between a Pokemon with 15 IVs and a Pokemon with 31 IVs is only 16 extra stat points so it really isn't that much compared to EVs and stuff. It really depends what you're using the Pokemon for. =)