If your like me, and you didnt get all the "kill X amount using specific gun" trophies, here are a few tips that might be helpful
First, try to do the gun specific trophies and challenges as soon as you get that power.
Leave all the target activities for gun kills, because that just makes it easier
If you did do all the target activities, hopefully you didnt unlock the kill bots (which come in fairly quickly if your leaving this for the last clean up)
Now again this might help if you did everything and are missing stuff
1) Go into a building. Most of the weak zin either run in or super run in, both of which is fine as its a confined space, and by now health shouldnt be a problem. ALso, lets say the portals are popping out kill bots. In a building the heat on you can decay, leaving more zin and less machines or flying guys.
2) Run away and wait till a portal opens up near you. If its zin, you can kill 2 towards what ever challenge or trophy your doing. Note that this works for both powers and guns. If that portal gives you kill bots, wait for another to arrive. This next portal is gaurenteed zin.
3) Combo your skills. Things like stomp are hard to do because most zin jump away. Freeze them, and then hopefully it counts as a stomp kill as well as a shatter
Last thing that isnt really a tip but a question.
I beat the game in 20 hours. Has anyone else had to grind out the time like i have? I am actually leaving it on all night tonight, just to get the last 8 hours i need. I did this for saint row 3 also, but now its 40 hours. I think the last time it was only 3o.