I'm not terribly good at making zoos (better with exhibit) so here's some exhibit tips
~I like to make a square exhibit, then make a large curved in viewing area, near the path side. Only the fences near the paths are glass/low/ though
~Make large exhibits. Don't worry to much about space - one of my best zoos only had three exhibits (savvanah rainforest and scrub if your wondering), but around 15 species of animals! SO yea, large exhibits = much goodness
~Water features. Like waterfalls. But don't put a waterfall in smaller exhibits, or it'll look crunched.
~For large wetlands exhibits, I like to make a river, and then a pond/lake surrounded by mangrove trees (except for where the river comes in). For smaller wetlands exhibits, you can still do it with no river.
~Mix animals! Don't be afraid to mix predator and prey. With the exception of reptiles - ALL of my reptiles constantly kill other animals and eachother ALL the time. If you want to, you can put in prey, wait till they reproduce and stuff, then put in predators, and the predators have to live off of eating prey, but only if you don't care what guests think. Guests get mad when they see animals being killed.
~When making waterfalls, don't just smooth the land around the waterfall, because it tends to make it look like a mound of dirt with water coming off the top. Make mesas(small platues) to give it a gently sloping, more natural feel.
~With wolves (but you can really do this with any animal) I like to make a 'feeding pit'. I make a small pit, and smooth the edges on one side, but not on the other, so there is one way out one way in. Then I put the food in there.
~If you have MM, make beaches! WIth otters, green turtles etc. I make flat land, then I make water. Then I make the water deeper, but so it's sloping gently. Viola, a beach.
~For wetlands, I like to make small pits and ditches and fill them with water, the slope the edges. It makes it look more below-sealevel like many swamps are. I make a lot of pits and many small pools
~With alpine, I like to make a mountain range. I make lots of steep cliffs, bluffs, peaks, summits, ledges, etc. But a cool thing about alpine is that it works well with other biomes. Around the mountains you could make small foothills, but I cover them and other low lands with grassland. The summits I cover with tundra snow. This design takes a lot of practice though.
Hope I could help some!