then considering everythig a alredy said you should add in your adsl router a static route to your lan subnet and set next hop (gtw) as 10.1.0.1/16 (your ZS)
as i can see you have a big network since you use class B subnet (16).
Consider the ability of your adsl router and hardware you run ZS on because it can slow down your network. If you network is not that big (more than 250 clients) you should use C class subnet (24).
hope this helps