Also, to make the final part of the lerp faster you can increase the destination value a bit. So if you want to zoom from 0.5 to 1, instead of this:
set scale to lerp(layerscale, 1, dt*10)
do this:
set scale to min(lerp(layerscale, 1.1, dt*10), 1)
lerp will be changing the scale to 1.1, but the min() function will stop it at 1.