There is a tech method, but it's significantly harder - you can practically blunder into the magic method but to do tech you need to get some cities up near the centre of the map, and have a suitable array of village spaces. The "treetop village" and "wooden city" are also slightly hidden, and it's not clear to me what lets a port city become a "mainport". "Adjacent" is misspelled in at least once place.
95, but frankly, while it helps to set up good shots, I think an awful lot of it once the red zombies come out is just luck in zombie placement. If you keep getting holes you can shoot through, you can do tremendous damage; a solid wall means turns sawing through it. Get lucky more often, like I just did, you can get a higher score.
Just won. On every level I either spammed interceptors or light carriers - try light carriers first if it's defence. Heavy Industry first, then upgrades to support those units. No economy, no turrets, no barriers. Forget clever strategy when you can bring a bigger hammer.
The good: I enjoyed this, and not merely because it's not another idle game.
The bad: it overstays its welcome at the end. There comes a point where you can't really expect to pull down more than 2 grand or so each run - whether or not you reach the final boss - and every upgrade costs a large multiple of that.
The rest: the Tesla connection is, ah, tenuous at best.
I just found myself on "2nd reset" after winning once. This is a bit vexing since even the earliest monsters in The Void and Land of the Dead have ludicrous combat abilities compared to my level-30 heroes.
 "Cyber Chaser"){kind=icon}
 "Home"){kind=icon}
 "Stop the Darkness"){kind=icon}
 "Where Are My Pets?"){kind=icon}
 "Balls vs Zombies"){kind=icon}
 "Tales of Nebezem: Golden Scepter"){kind=icon}
 "Frog Fable"){kind=icon}
 "No Time To Explain"){kind=icon}
 "Obliterate Everything 2"){kind=icon}
 "Feed The D (Christian-Friendly)"){kind=icon}
 "Tesla8"){kind=icon}
 "Cube Escape: Birthday"){kind=icon}
 "Idle Sword"){kind=icon}
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 "Excavate!"){kind=icon}
 "League of Angels"){kind=icon}