OP, you're talking more about Jeff for the fill-in role for the rest of the tour in 82? Reason I ask is that I don't remember him having a lot of credit as a writer with Night Ranger, so different question for me if it's fill-in versus permanent replacement (I'm thinking from your comments above on Jake and Zakk though this is more of a fill-in question). I know what you are saying on Jeff's technique though, although I actually think Brad did a pretty good job on the Randy material based on how little time he had to prepare.
Obviously Zakk was not actually in the mix as a replacement at the time, he was 15 and wouldn't join the band until 6 years later. His playing at that time really fit the band because in 88, the times were already changing and he had a fresh sound during a period when things were getting stale. I'm reading the OP's comment on Zakk as a general looks thing, not as an actual "the best replacement for Randy" whether fill-in or otherwise.