The only way I can manage it with 4 small boys is to have a really strict routine, not deviate from my times that I have to do things by, and I do everything in "shifts"!!
I feed DS1(5 years) DS2(4 years-last week) and DS3(16 months) together at about 4.30pm
I bath DS3 and put him to bed at 5pm ( I know that seems early but he likes his sleep and is quite happy playing in his cot until he nods off)
I then feed DS4 (12 weeks) at 5pm while DS1 sits next to me and reads me his school reading book (and DS2 normally sits the other side of him and listens to the story too)!!
I then change DS4 and put him on his playmat for a kick around.
DS1 & DS2 watch Backyardigans on Nick JR while I clear up the dinner things, load the dishwasher and run their bath so that as soon as that finishes (about 5.50pm) they come up and get in the bath.
After their bath they watch the second story of Fifi & the Flowertots and Pick Me. At 6.25pm we go up to their room and they have about 10 pages of a story and go to sleep at 6.30pm (although DS1 normally doesn't nod off until nearly 7pm)
At 6.30pm I come down and check on DS4 who is normally asleep under the playmat by now!! I clear up what mess is left lying around, bung the clothes in the wash, clean and sterilise the bottles and start dinner for myself and DH.
It sounds a lot more organised than it is and DS4 is only 12 weeks so you can't rely on him to keep in routine quite as well as the others and every now and again it all goes pear shaped. As a rule it works and I am free to spend time with DH from 6.30pm