Compare the pricing from Zen to the pricing from someone else. Should be pretty simple math to figure out whether paying Zen's monthly fee and transaction fees are greater than or less than paying someone else's monthly fee and transaction fees.
With Zen, you get an account with a financial institution that's comfortable with some forms of
high risk business. They also appear quite stable. Zen has access to more currencies than many EMIs, and offer pretty decent FX rates. All that is worth paying for.
How many mishaps/delays with another institution would it take for the 1,800 EUR/year with Zen to have been worth it? How much are you losing in FX with another institution that you could save with Zen? For many businesses, that would pay for itself in less than a month.
I know people happily paying far more than 150 EUR/month for accounts with Zen. I also know some businesses have no need for what Zen can offer.