Kohlschreiber opened the best-of-five series by sweeping Roberto Bautista Agut 6-2, 6-4, 6-2 and Mayer followed with a 7-6 (8-6), 7-6 (7-4), 1-6, 7-5, 6-3 win, while recording just one break of serve.
Sunday's reverse singles opens with Kohlschreiber facing Lopez and wraps with a Mayer-Bautista Agut match.
The winner between Spain and Germany gains a quarterfinal spot against the winner of the series sending Australia against France. France is up 2-0 in that series.
Mayer missed out on five break opportunities but used success in the tiebreakers to take a 2-0 set lead. Lopez used the first two breaks of the match to win the third set and four off four more break points in forcing a fifth set.
Mayer -- on his 10th try -- finally finished off a break opportunity and then held on for the 2-0 series lead.
Kohlschreiber didn't allow Bautista Agut a break chance the entire match, winning 72 percent of the points on serve. He converted five of his eight break chances, including two in the final set.