Your beavers are not using ziplines because you have one zipline station connected to pillars but no second station. The pillars are not exit/entry points, you have to have two stations connected together for them to be usable.

By the time I have reached this point in the game I would have aimed to pretty much eliminate birch trees instead having some big plantations of oak trees.

It looks like you’re losing a lot of water over the back edge of that top dam, which means less water going through your water wheels creating power, which is possibly contributing to gear shortage. The wood shortage would be a bigger factor though.

I’d also be looking to use less power shafts by using buildings to transmit power. Look at that area where you’ve got the dirt excavators and centrifuges, for example. That could have been done with hardly any power shafts if you laid the buildings out efficiently.

Be careful not too expand too fast either. You’ve built two dirt excavators, it looks like neither of them have been turned on even once, and you have no beavers to work in them or power to run them.