I recently received Zendikar Resurgent, however this card feels very underpowered for a Mythic.
Lets compare it to 2 other cards:
Shrine Of The Forsaken Gods and Prism Array
All 3 of these cards have a shield value of 3, so that will not be considered.
Shrine Of The Forsaken Gods is rare costs only 6 and is colorless. After 2 turns, you will already already have a gain, even more gain with colorless cards and a bit of luck.
Prism Array is rare and only costs 6. There is a bit of luck involved, but it provides the ability to disable creatures draw many cards. Also this can trigger on either your turn or the AI’s turn. And the AI almost always goes for match 4/5s.
Zendikar Resurgent costs 14. For the mana gain aspect, you would have to make a minimum of 7 matches, just to break even. Now this does come with a card draw every time you play a creature. But there are much better ways to draw cards, without relying on playing creatures.
Overall I think Zendikar Resurgent is a decent card, but when compared to rare supports, it feels very under powered for a mythic.
I would suggest either lowering the casting cost and/or increase the mana gain portion.