Here's a video in case the written instructions weren't very clear:The quick and easy way!
This achievement requires that you only use "large" monkeys, as in how much space they occupy. Pat Futsy, Helicopters, Buccaneers, Villages, etc.
So how I unlocked mine was this way:
1. Pick any easy map, and choose Deflation. (It's also possible with most other game modes, but Deflation is the quickest and easiest.)
2. Use Pat Futsy as your hero, and set him to "Strong".
3. Get 4 helicopters, and upgrade them to 3-2-0 (So you have Razer Rotors and IFR.)
4. Press play, fast forward, and after a little while you'll have finished the map.
Do this 10 times and the achievement will be yours! 🎉