I have been looking in the manual but I can’t find anything saying I can’t. Is it legal to end on their home zone?
Well, you could, but you would automatically forfeit the autonomous bonus to your opponent if you did because you entered their home zone
SG4 should answer that for you.
Violations of this rule will result in the Autonomous Bonus being awarded to the opposing Alliance. The opposing Alliance will also receive an Autonomous Win Point, regardless of whether they completed the Autonomous Win Point tasks. Intentional, strategic, or egregious violations, such as intentional contact with an opposing Robot completely within their Alliance Home Zone, will result in a Disqualification.