If you look at their guidance for 2019, you'll notice they did not forecast EBITDA to increase. If you look at their statements, you'll also notice cash + cash equiv decreased by >90% while PPE increased by ~$30M. I suspect this is due to their winning of some major contracts requiring some heavy initial capital outlay, to fulfill their BOO model.
Based on this, I believe the SP will move largely sideways within the 59 - 65 range for the next 12 months, as investors believe their money is better elsewhere. I suspect 2020 will be a good year for ZEN.