How do I calculate the cost basis of Restricted Stock Units (RSUs)?

I was granted RSUs that vested 1/3 per year, over 3 years. From E*Trade I have:

• 2016, 133 Shares Vested, 89 Shares Transferred to me, Tax Paid: $3,424.52
• 2017, 134 Shares Vested, 90 Shares Transferred to me, Tax Paid: $4,795.56

In 2017 I sold all of these, with proceeds of $7,814.83 and $10,709.51 respectively.

Since the original shares were already taxed (I vested 133 and 134, but x-shares were sold for tax purposes, noted above), do I put a cost basis of $0 on the remaining proceeds I received after selling what was left over?

Update

For completeness, here’s my RSU history and how I filed:

Vesting #1 | 133 Shares
------------------------
Vest Date:    07/16/2016
PPS at Vest:  $77.83

Shares Assigned:           89
Shares Witheld for Tax:    44
Total Tax Paid (at vest):  $3,424.52
Cost Basis:                $6,926.87

Sale Date:    02/15/2017
PPS at Sale:  $87.95


Vesting #2 | 134 Shares
------------------------
Vest Date:    07/16/2017
PPS at Vest:  $108.99

Shares Assigned:           90
Shares Witheld for Tax:    44
Total Tax Paid (at vest):  $4,795.56
Cost Basis:                $9,809.10

Sale Date:    08/17/2017
PPS at Sale:  $116.47