If the new job is equally skilled, and the company is equally sound, it would still count towards the same Residence application. The part of the case concerned with checking out the details of the job and the company would have to be done for the new employer, but all the rest of your details remain the same. Even if taking a new job would move you into the territory of a different INZ office, and INZ transferred your case, everything already done on your application is on record and would stand - a new CO never has to start from zero if they take over a partly-done application.
It might be worth contacting your CO and asking a 'what if?' question. I'm thinking, suppose you went for the new job offer. How long would it take to make the change, by the time you'd worked out your notice, moved house, and started? - several weeks? a couple of months? You could tell the CO you're thinking of applying for a different job in that next period of time, and because they will want to know your visa status, you wonder whether she could give you an idea of when your application will be settled.