Looks like you double up on roads and rails; that was going to be my next plan. Also your zone squares are smaller; I've been going six by six, and even bigger on the cost lines because it can be a bitch to put roads and rails on the coast.
Do you progress to denser zones as you move across the map or do you replace lighter ones with denser ones as you gain in population and profit?
And I hope you don;t mine me pestering you with this stuff. :P
Lol pestering, as if :) I'm sure bigger zones could work, with a sufficient transportation/road system. But I like to keep industrial zones 3x3 though, and later 4x4, so that each block is eventually taken up by a single building.
I don't really change the zone intensity much afterwards. The exception is for industrial zones and zones placed early game when cash is in short supply. When I create a new block I plan it as a low density block, or a medium density block, or a high density block. But because of cash shortages in the beginning I have to use low density housing for areas I intend to be higher density, until I can afford to demolish and replace it. The planning comes in for working out separation between the blocks because I put rail way lines between the blocks: one between a low density block and the wilderness, two between a low density block and medium density block, and 3 between two medium density blocks. High Density blocks get surrounded by highways instead. I'm not saying this is the best way. It's just what I'm trying out at the moment.
Three railway lines take up a lot of space if you separate them with one space to keep them from forming weird looking loops, but you can win back that space later on with tunnels once you can afford it. Subways would be cheaper than tunnels (weirdly), but I like the look of rail tracks :P It doesn't make sense to me for downtown suburbia to have subways :P