Zack and the terrible, horrible, no good, very bad day

Sounds kind of boring, right? Well, read it anyway, because I just don't know what to do with this child sometimes!! Sorry it's kind of long, though.

The following is a conversation held by Zack (Z) and Mommy (M) on Tuesday evening regarding his homework assignment to draw a picture, label it and write 1-3 sentences (of which he is perfectly capable):

Z-I don't know what to write about.
M-Well, what happened at school today?
Z-We had fun.
M-What were you doing?
Z-Playing in the gym
M-What were you doing in the gym?
Z-We were playing "cross the ocean."
M-Can you tell me about it? (At this point, I heard the teacher in me talking.)
Z-It's a game where you have to cross the ocean. The floor is the ocean and you have to stay away from the sharks. Those are the people who are "it."
M-Oh, so it's kind of like a tag game.
Z-Yeah. If you get tagged by a shark, you have to sit on the floor like this (sat down and waved his arms out to the side).
M-Do you turn into a fish?
Z-No, you're a jellyfish.
M-So you get to tag people when you're a jellyfish?
Z-Yeah.
M-Okay, well that's a great story. Let me get you a piece of paper so you can draw your picture.
Z-That'll be a lot of people to draw.
M-That's okay, you don't have to draw all of them.

...A few minutes later, after he had been working on it, I went back to check on him. He had drawn a floor and two walls. In the middle was a stick figure whose arm was stretched out like he was trying to tag someone. (sorry, we got a bit more)
M-That looks good, I like how that person is reaching out to tag someone.
Z-Yeah, I don't like it. You can't see his smile.
M-Well, his head is really small, it's okay that you can't see it.
Z-But his legs don't look right. They're not the right size. And I don't have room to draw everybody. But we had to sit on the stage because there were too many people playing.

I wanted to help, but I also wanted us to be done with homework, so I added the stage to his drawing with a person sitting criss-cross.
Z-But their legs were hanging down. (I fixed it.)
Z-But his arms don't look right and I can't draw the other people.
M-(getting frustrated but trying to stay calm)Okay. Since we're getting frustrated with the drawing, let's just work on the words. You can write the story.
Z-I don't know what to write.
M-Write what you told me. "I had fun in the gym today. We played cross the ocean." Then keep going. (I even tried to encourage him that that was a great beginning and that I used to teach my first graders things like that.)

(I promise, it's almost done.) Well, it went all downhill from there...Instead of writing his story, he was scribbling on his paper. Then I found him playing in his room, saying he was doing something to write about. He was knocking over the chair, banging stuff, fussing and crying about getting it done! Mark took over, but it didn't really help. We did find out that Zack didn't really get to play the game, that he had to sit on the stage most of the time because he was tagged early in the game. Zack was eventually sent to time-out, where he cried and screamed that he didn't want to be bored anymore. Mark finally said, "Ok, if you're not going to do your homework, I'll tell you what to write and you'll write it." That's what happened, and this is what he wrote: "I was really grumpy after school today. I got angry doing homework. Daddy told me what to write." Yup, that's what he turned in, with a picture of himself on the top with a very sad face.

I went to work that night with a pain in my middle back that I attributed to the stress of a child crying about homework (and another child miserable with a cold, whining about not wanting to eat). Of course I want Zack to be happy, but I'm getting to the end of my rope. Mark said last night that Zack is going to hate school by the end of the year. I dread homework time everyday because I know it's going to be difficult, no matter how hard I try to be nice and reasonable.

So I guess I'm looking for 1. a way to make homework time NOT be a battle of wills and 2. reassurance that this is going to get better. Oh, and any suggestions on how to help him make friends, besides making playdates. (We would love to do that, but our question would be who to invite or how would I contact the parent?) He's lonely and unhappy, and I wonder if he's sometimes depressed. Help me help my little boy!