The plugin handles requotes only insofar as Zorro is notified about them and can then decide in the script what to do. The Z scripts do not enter trades again in case of a requote. Requotes can thus indeed reduce the performance.

For preventing requotes, edit zorro.mq4 and set the "#define SLIPPAGE 10" line to a higher value, such as 30 or 50 instead of 10. In the next update, this value can be determined in pips and will adjust to the number of price digits by the broker.