billnet, 我倒戈啦，哈哈。

同意你说的iz比is容易，从语言学的角度，in iz, both the vowel and the z are voiced. So to make the sound iz, the vocal cords do not need to switch from voiced to voiceless. But, there are a lot of languages that have the rule of final devoicing, which is the case in iz changing to is. There are linguists who thinks that final devoicing is caused by not sufficient air flow to maintain the voicing, i.e. to keep the vocal cords vibrating.