Work with the customer more closely.
Tell them you need the site by yourself until XYZ date. If you can't get done by then, you are gonna need to work around other contractors.
For tree protection zones, The client HAS to be the one putting the pressure on the contractor. They are going to ignore us every time because we are nothing more than a nuisance. Put up construction fence. Tell the client to put a fine in their contract if that area is violated. Probably helps to be a little over dramatic (without being a jerk) the first time you see a minor violation of that. Lots of mulch (that is going to be pulled away later) to prevent compaction if you know they have to be on the roots with equipment.