I2C communication not working
The voltage you see on your bus line corresponds to a resistance of the low side switch of something above 200 ohm.
A quick glance in the schematic of the ZedBoard shows, that some input pins have a 200 ohm series resistor, probably for ESD protection. I assume you used such a pin for your I2C communication, but since you did not tell us how exactly you connected the µC to the ZedBoard I can't say for sure.
You will have to use an input pin without this series resistance to get a good low level.