There is no fixed maximum in ZBS. However, when editing rules they are all assembled in JavaScript in your web browser, so the speed of an older PC may make it tiring to deal with very large numbers of rules.

My main PC is 4 year old (was top spec then) and starts to slow a little when there are about 150 rules, but I have kept on going to well past 200 rules and it continues to work.

Having said all that, unless you have a very unusual shipping requirement, if you find you rules creeping up to those sorts of numbers there is probably a better way of analysing your shipping requirements to reduce the number of rules.

If you have rules that are getting out of hand, please open a support request, describe what you are trying to achieve and attach screenshots and I can advise on ways to get them organised.

v1.7 of ZBS introduces excess shipping costs which can be used to cut down on repetition in rules.

http://www.concrete5.org/marketplace/addons/zone-based-shipping/for...