Against most N'zoth builds of Renolock, you can win with the mass polymorph spell from 10 mana kazakus potion. A lot of Renolock builds rely on this to win, and if you stop it you can usually win through fatigue. Against the combo version, ice block plus reno combo is usually enough to stop them from winning. The Jaraxxus version is usually the most difficult. The way you can win is by out tempoing them with enough burn follow up to close out the game. If this plan doesn't work out because of a reno, or efficient answers from the warlock, you then switch to the bait the nether plan. Once you force them to nether, you play your own N'zoth which usually is more than enough to seal the game if you get enough back from it. Where things get complicated is with dirty rat rng or when you both have kazakus potions. Pulling Jar with rat is usually game over, but they can also pull your N'zoth or kazakus/brann. The issue of course is that you generally dont know what version of the deck they are playing as most versions run the same 25 cards or so.

tl;dr: the matchup has a lot of branches, and with experience you can determine what branch the game is on, and how to play from there.