z-scores using glht

Hi all,

after fitting a model with lme, I run post-hoc tests with glht. The results
are repored in the following:

lev.ph <- glht(lev.lm, linfct = ph_conditional);
summary(lev.ph, test=adjusted("bonferroni"))

Simultaneous Tests for General Linear Hypotheses

Fit: lme.formula(fixed = data ~ des_days, data = data_red_trf, random =
~des_days |
    ratID, method = "ML", na.action = na.omit, control = lCtr)

Linear Hypotheses:
                                 Estimate   Std. Error  z value
Pr(>|z|)
des_days1 == 0     3232.2      443.2         7.294        9.05e-13 ***
des_days14 == 0   3356.1      912.2         3.679        0.000702 ***
des_days48 == 0   2688.4     1078.5        2.493        0.038025 *

I am trying to understand the output values. How are the z-scores computed?
If the function uses standard errors, should these be t-statistics (and not
z-scores)?

Sorry for the perhaps trivial question.

Best