I don't have a Mimeoplasm deck, so I can easily be wrong, but if you choose to play
Green Sun's Zenith you should add
Dryad Arbor and
Bloom Tender (
Birds of Paradise are already there).
Tender gives you a lot of mana and Arbor could be always sacrified to
Victimize.
I would prefer
Swan Song to
Counterspell because you won't have 2 blue mana open that often, especially when comboing off.
As for the lands, I prefer
Underground River to
Choked Estuary (and
Llanowar Wastes and
Yavimaya Coast to
Twilight Mire and
Flooded Grove) as I personally rank pain lands after duals and shock-lands but before check-lands and hybrid-lands.
Also, if you play
Life from the Loam I will recommend you the cycling lands from
Onslaught and, as you're already playing several tapped lands, I would try
Amulet of Vigor, although it's better in decks with more ramp.
Another good card with Loam is
Oona's Grace.
At first it's a bit costy, but it turns all your lands into cycling cards, giving you a lot of value.
I used to play
Trade Routes but ended up with Grace because it gives a card since the first cast and it's never
dead, even when you happen to throw it to the bin.