Trivial difficulty: 4 cannons without phases (No terminator chickens)
Easy difficulty: 5 cannons with only one phase for summoning terminator chickens (Phase starts at 50%)
Intermediate difficulty: 5 cannons with 2 phases (33% and 66%)
Hard difficulty: 6 cannons with 2 phases
Very hard difficulty: 6 cannons with 3 phase (same as the default)
Elite difficulty: 7 cannons with 3 phase
P.S. Both Yolk Star and Egg Cannon should drop a satellite (like Henterprise), when the shell of Tge Yolk Star is cracked or the purplish explotion of Egg Cannon. (Thanks to @B256 for reminding)
I hope you interested with this and share your comments. Thanks! (And sorry, if I made mistakes about difficulty percents)
Maybe the satellite drop for the yolk star is base on it difficulties. (Easy: Each 20%, Hard: Each 33%) Except very Hard: Each 40%. Since I think it will be very hard if the very hard satellite drop 50%.