Your current employer is giving you an effective 8 year vesting schedule, no one would JOIN a company on those terms. Alternatively, you can look at it like they don't value your first 4 years of contributions at all towards to the value of the company.

Echoing the $0 valuation comment, which you should heed: $60k guaranteed per year is astronomically difficult to match with illiquid equity. You need only search for "equity" here on HN to read the multitude of warnings against overvaluing (read: valuing at all) your equity.